Polyurethane adhesive layers for electro-optic assemblies

ABSTRACT

Electro-optic assemblies and related materials (e.g., adhesive) for use therein are generally provided. The adhesive layer may comprise an end-capped polyurethane. Some adhesive layers comprise two or more reactive functional groups (e.g., reactive functional groups configured to react with one or more curing species such that, for example, at least one of the two or more functional groups forms a crosslink). The adhesive may also comprise a chain-extending reagent that includes one or more reactive functional groups. In some embodiments, the adhesive is cured by reacting one or more reactive functional groups with one or more curing species. Curing the adhesive may comprise two or more curing steps. In some embodiments the adhesive layer may comprise one or more cross-linkers.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application Ser. No.62/235,480, filed Sep. 30, 2015 and U.S. Application Ser. No.62/235,580, filed Oct. 1, 2015. The entire contents of bothapplications, and of all other U.S. patents and published and copendingapplications mentioned below, are herein incorporated by reference intheir entireties.

BACKGROUND

Polyurethanes find uses in a wide variety of applications, for example,for use as adhesives. The adhesives may be utilized in electro-opticassemblies, wherein the electro-optic assemblies generally comprise aplurality of functional layers and can be used to form displays such aselectrophoretic displays. Such assemblies may include a layer ofelectro-optic material, a front plane and a backplane. Electro-opticmaterials generally have at least two display states differing in atleast one optical property (e.g., optical transmission, reflectance,luminescence) when different electric fields are applied to thematerial. Electro-optic displays can have attributes of good brightnessand contrast, wide viewing angles, state bistablility, and low powerconsumption.

In some instances, electro-optic assemblies utilize an adhesive toadhere different layers together (e.g., the electro-optic material layerto the front plane and/or the backplane). Such adhesives are generallyknown in the art and may comprise, for example, hot-melt type adhesivesand/or wet-coat adhesives, such as polyurethane-based adhesives.Adhesives generally require good strength of adhesion, while havingcertain properties (e.g., electrical properties, mechanical properties,thermal properties) that do not hinder the operation of theelectro-optic display. However, there remains a need for adhesives withimproved properties.

SUMMARY

The invention is a polyurethane adhesive material for use inelectro-optic assemblies. The polyurethane adhesives typically includeat least an end-capping cyclic carbonate group, however, they mayinclude additional functional elements and/or cross-linkers. In someembodiments, the adhesive is formed by two or more curing steps. Eachcuring step may comprise, for example, crosslinking of the adhesive,thermoplastic drying of the adhesive, end-capping the adhesive,chain-extending the adhesive, and/or combinations thereof such that theadhesive undergoes at least one cure in each curing step.

In one aspect, polyurethane adhesive layers are disclosed for the use inelectro-optic assemblies. In some embodiments, the polyurethane a cycliccarbonate end-capping group. In some embodiments, the adhesive comprisespolyurethane and acrylic functional groups. In some embodiments, theadhesive comprises a first reactive functional group, and a secondreactive functional group, wherein at least one of the reactivefunctional groups has a dipole moment of greater than about 2 Debyes.

Other aspects and various non-limiting embodiments of the invention aredescribed in the following detailed description. In cases where thepresent specification and a document incorporated by reference includeconflicting and/or inconsistent disclosure, the present specificationshall control. If two or more documents incorporated by referenceinclude conflicting and/or inconsistent disclosure with respect to eachother, then the document having the later effective date shall control.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments of the application will be describedwith reference to the following figures. It should be appreciated thatthe figures are not necessarily drawn to scale.

FIGS. 1A-1E are schematic illustrations of electro-optic assembliescomprising an adhesive layer.

FIG. 2 exemplifies end-capping reagents that may be used in the creationof adhesive layers for electro-optic assemblies.

FIG. 3 exemplifies chain-extending reagents that may be used in thecreation of adhesive layers for electro-optic assemblies.

FIG. 4 exemplifies reactions that can be used for curing an adhesivelayer in an electro-optic assembly.

FIG. 5A is a plot of adjusted white state (WS) 30 s image stability ofexperimental polyurethanes overcoated on an electro-optic layer.

FIG. 5B is a plot of adjusted dark state (DS) 30 s image stabilitytraces of experimental polyurethanes overcoated on an electro-opticlayer.

FIG. 6 is a plot of adjusted 30 s white state (WS) image stability foradhesive overcoated to an electro-optic layer with various levels ofcyclic carbonate end groups (CCARB).

FIG. 7 is a plot of drift in adjusted 30 s WS L* versus mole % cycliccarbonate end cap group for adhesives overcoated to an electro-opticlayer. FIG. 7 suggests an optimal range of cyclic carbonate to reduce 30s WS L* drift.

FIG. 8 is a plot of drift in adjusted 30 s WS image stability forpyrrolidone (HEP) and cyclic carbonate (CCARB) adhesives overcoated onan electro-optic layer.

FIG. 9 is a plot of WS L* versus pulse length for a standard aqueouspolyurethane dispersion adhesive (control) and a cyclic carbonatepolyurethane adhesive with acid functionality (CCARB/Acid). Bothadhesives were overcoated to an electro-optic layer compared with anaqueous polyurethane dispersion (control) laminated to the same ink,according to one set of embodiments;

FIG. 10 is a plot of White State (WS) drift in L* (L*δWS) versuselectrical stress time at 25° C. for polyurethane adhesive layerscomprising a variety of functional groups.

FIG. 11 is a plot of WS 30 second adjusted image stability traces forcyclic carbonate polyurethane (CCARB) coated at low and high dryadhesive coat weights compared to a commercially-available aqueouspolyurethane dispersion adhesive coated at approximately 4 mil.

FIG. 12 shows Storage (G′) and Loss (G″) shear modulus curves at 1 Hzfor hybrid polyurethane adhesives cured through stage I (“first cure”)and stage II (“second cure”).

FIG. 13 is an SEM micrograph at 100× magnification of anelectrode/electro-optic layer/adhesive layer stack with a hybridadhesive coated at 8 g/m², after curing. This micrograph illustratesthat the adhesive layer can be applied at good planarity and withminimal increase in the overall thickness of the stack.

FIG. 14 is an SEM micrograph at 1000× magnification of anelectrode/electro-optic layer/adhesive layer stack with a hybridadhesive coated at 8 g/m², after curing.

FIG. 15 shows exemplary schemes for reacting a polyurethane (PU) withcrosslinkers.

FIG. 16 is a plot of the Storage (G′) and Loss (G″) shear modulus curvesat 1 Hz for uncured and cured (through stage II) cross-linked cycliccarbonate polyurethane (X-CCARB) adhesive.

FIGS. 17A-17B are SEM micrographs at 100× and 1000× magnification,respectively, of electrode/electro-optic layer/adhesive layer stack witha cross-linked cyclic carbonate polyurethane coated at 7 g/m², aftercuring, illustrating that the overall thickness of the electro-opticlayer is increased only minimally with the inclusion of the adhesive.

Other aspects, embodiments and features of the invention will becomeapparent from the following detailed description when considered inconjunction with the accompanying drawings.

DETAILED DESCRIPTION

The invention includes a new class of polyurethane adhesive layers thatare well-suited for incorporation into electro-optic assemblies, forexample, encapsulated electrophoretic displays. The polyurethaneadhesives typically include at least a cyclic carbonate group, however,they may include additional functional elements and/or cross-linkers. Insome embodiments, the adhesive is formed by two or more curing steps.Each curing step may comprise, for example, crosslinking of theadhesive, thermoplastic drying of the adhesive, end-capping theadhesive, chain-extending the adhesive, and/or combinations thereof suchthat the adhesive undergoes at least one cure in each curing step.

The adhesive may comprise at least one type of end-capping reagentand/or at least one type of chain-extending reagent. In certainembodiments, the adhesive comprises two or more reactive functionalgroups (e.g., reactive functional groups configured to react with one ormore curing species such that, for example, at least one of the two ormore reactive functional groups forms a cured moiety such as acrosslink). The adhesive, in some cases, comprises an acrylic. Incertain embodiments, the adhesive is a hybrid adhesive comprising two ormore types of adhesive materials (e.g., a hybrid adhesive comprising apolyurethane and an acrylic). In some embodiments, the adhesive isformed by the curing of two or more adhesive materials under twodifferent sets of conditions. For example, in an exemplary embodiment,the adhesive comprises an acrylic cured via thermoplastic drying and apolyurethane cured via reaction with the acrylic (e.g., via crosslinkingwith the acrylic).

Methods for forming adhesives and adhesive layers are also generallyprovided. In some embodiments, the method comprises curing an adhesiveby reacting one or more reactive functional groups with one or morecuring species (e.g., reacting the adhesive with a first curing speciesand, subsequently, reacting the adhesive with a second curing species).For example, curing the adhesive may comprise crosslinking the adhesiveby reacting one or more reactive functional groups with a curing speciessuch as a crosslinking reagent. Reactive functional groups and types ofcuring species are described in more detail, herein. In some cases,curing the adhesive may comprise crosslinking of the adhesive,thermoplastic drying of the adhesive, end-capping the adhesive,chain-extending the adhesive, and/or combinations thereof. In certainembodiments, curing the adhesive comprises a first curing step and asecond curing step (e.g., wherein each curing step comprises reacting areactive functional group with one or more curing species). In somecases, a substrate (e.g., a release layer, an electro-optic layer) isadhered to the adhesive after the first curing step and before thesecond curing step.

The adhesives may be useful in a number of applications, including, butnot limited to, materials for use in electro-optic assemblies (e.g., asadhesive layers). The electro-optic assemblies may form an electro-opticdisplay such as an electrophoretic display. As described above,electro-optic assemblies generally comprise a plurality of functionallayers including, but not limited to, a front plane electrode (e.g.,which may comprise a polymeric film coated with a conductive material),a backplane electrode (e.g., which may comprise an electrode, circuitry,and/or a support layer) and an electro-optic material layer. Theelectro-optic material layer can comprise an electro-optic materialhaving first and second display states differing in at least one opticalproperty (e.g., optical transmission, reflectance, luminescence), thematerial being changed from its first to its second display state byapplication of an electric field to the material. For example, in someelectrophoretic displays, the electro-optic material layer may include aplurality of capsules that are distributed in a binder. The capsules caninclude a clear fluid in which electrically-charged ink particles (e.g.,black and white ink particles) are suspended. The ink particlestranslate within the capsule in response to electric fields to producean image that is displayed.

The term “electro-optic”, as applied to a material or a display, is usedherein in its conventional meaning in the imaging art to refer to amaterial having first and second display states differing in at leastone optical property, the material being changed from its first to itssecond display state by application of an electric field to thematerial. Although the optical property is typically color perceptibleto the human eye, it may be another optical property, such as opticaltransmission, reflectance, and luminescence or, in the case of displaysintended for machine reading, pseudo-color in the sense of a change inreflectance of electromagnetic wavelengths outside the visible range.

The term “gray state” is used herein in its conventional meaning in theimaging art to refer to a state intermediate two extreme optical statesof a pixel, and does not necessarily imply a black-white transitionbetween these two extreme states. For example, several of the E Inkpatents and published applications referred to herein describeelectrophoretic displays (EPIDs) in which the extreme states are whiteand deep blue, so that an intermediate “gray state” would actually bepale blue. Indeed, as already mentioned, the change in optical state maynot be a color change at all. The terms “black” and “white” may be usedhereinafter to refer to the two extreme optical states of a display, andshould be understood as normally including extreme optical states whichare not strictly black and white, for example the aforementioned whiteand dark blue states. The term “monochrome” may be used hereinafter todenote a drive scheme which only drives pixels to their two extremeoptical states with no intervening gray states.

The terms “bistable” and “bistability” are used herein in theirconventional meaning in the art to refer to displays comprising displayelements having first and second display states differing in at leastone optical property, and such that after any given element has beendriven, by means of an addressing pulse of finite duration, to assumeeither its first or second display state, after the addressing pulse hasterminated, that state will persist for at least several times, forexample at least four times, the minimum duration of the addressingpulse required to change the state of the display element. It is shownin U.S. Pat. No. 7,170,670 that some particle-based electrophoreticdisplays capable of gray scale are stable not only in their extremeblack and white states but also in their intermediate gray states, andthe same is true of some other types of electro-optic displays. Thistype of display is properly called “multi-stable” rather than bistable,although for convenience the term “bistable” may be used herein to coverboth bistable and multi-stable displays.

Several types of electro-optic displays are known. One type ofelectro-optic display is a rotating bichromal member type as described,for example, in U.S. Pat. Nos. 5,808,783; 5,777,782; 5,760,761;6,054,071 6,055,091; 6,097,531; 6,128,124; 6,137,467; and 6,147,791(although this type of display is often referred to as a “rotatingbichromal ball” display, the term “rotating bichromal member” ispreferred as more accurate since in some of the patents mentioned abovethe rotating members are not spherical). Such a display uses a largenumber of small bodies (typically spherical or cylindrical) which havetwo or more sections with differing optical characteristics, and aninternal dipole. These bodies are suspended within liquid-filledvacuoles within a matrix, the vacuoles being filled with liquid so thatthe bodies are free to rotate. The appearance of the display is changedby applying an electric field thereto, thus rotating the bodies tovarious positions and varying which of the sections of the bodies isseen through a viewing surface. This type of electro-optic medium istypically bistable.

Another type of electro-optic display uses an electrochromic medium, forexample an electrochromic medium in the form of a nanochromic filmcomprising an electrode formed at least in part from a semi-conductingmetal oxide and a plurality of dye molecules capable of reversible colorchange attached to the electrode; see, for example O'Regan, B., et al.,Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24(March 2002). See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845.Nanochromic films of this type are also described, for example, in U.S.Pat. Nos. 6,301,038; 6,870,657; and 6,950,220. This type of medium isalso typically bistable.

Another type of electro-optic display is an electro-wetting displaydeveloped by Philips and described in Hayes, R. A., et al., “Video-SpeedElectronic Paper Based on Electrowetting”, Nature, 425, 383-385 (2003).It is shown in U.S. Pat. No. 7,420,549 that such electro-wettingdisplays can be made bistable.

One type of electro-optic display, which has been the subject of intenseresearch and development for a number of years, is the particle-basedelectrophoretic display, in which a plurality of charged particles movesthrough a fluid under the influence of an electric field.Electrophoretic displays can have attributes of good brightness andcontrast, wide viewing angles, state bistability, and low powerconsumption when compared with liquid crystal displays. Nevertheless,problems with the long-term image quality of these displays haveprevented their widespread usage. For example, particles that make upelectrophoretic displays tend to settle, resulting in inadequateservice-life for these displays.

As noted above, electrophoretic media require the presence of a fluid.In most prior art electrophoretic media, this fluid is a liquid, butelectrophoretic media can be produced using gaseous fluids; see, forexample, Kitamura, T., et al., “Electrical toner movement for electronicpaper-like display”, IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y.,et al., “Toner display using insulative particles chargedtriboelectrically”, IDW Japan, 2001, Paper AMD4-4). See also U.S. Pat.Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic mediaappear to be susceptible to the same types of problems due to particlesettling as liquid-based electrophoretic media, when the media are usedin an orientation which permits such settling, for example in a signwhere the medium is disposed in a vertical plane. Indeed, particlesettling appears to be a more serious problem in gas-basedelectrophoretic media than in liquid-based ones, since the lowerviscosity of gaseous suspending fluids as compared with liquid onesallows more rapid settling of the electrophoretic particles.

Numerous patents and applications assigned to or in the names of theMassachusetts Institute of Technology (MIT) and E Ink Corporationdescribe various technologies used in encapsulated electrophoretic andother electro-optic media. Such encapsulated media comprise numeroussmall capsules, each of which itself comprises an internal phasecontaining electrophoretically-mobile particles in a fluid medium, and acapsule wall surrounding the internal phase. Typically, the capsules arethemselves held within a polymeric binder to form a coherent layerpositioned between two electrodes. The technologies described in thethese patents and applications include:

(a) Electrophoretic particles, fluids and fluid additives; see forexample U.S. Pat. Nos. 7,002,728; and 7,679,814;

(b) Capsules, binders and encapsulation processes; see for example U.S.Pat. Nos. 6,922,276; and 7,411,719;

(c) Films and sub-assemblies containing electro-optic materials; see forexample U.S. Pat. Nos. 6,982,178; and 7,839,564;

(d) Backplanes, adhesive layers and other auxiliary layers and methodsused in displays; see for example U.S. Pat. Nos. 7,116,318; and7,535,624;

(e) Color formation and color adjustment; see for example U.S. Pat. No.7,075,502; and U.S. Patent Application Publication No. 2007/0109219;

(f) Applications of displays; see for example U.S. Pat. No. 7,312,784;and U.S. Patent Application Publication No. 2006/0279527; and

(g) Non-electrophoretic displays, as described in U.S. Pat. Nos.6,241,921; 6,950,220; and 7,420,549; and U.S. Patent ApplicationPublication No. 2009/0046082.

Many of the aforementioned patents and applications recognize that thewalls surrounding the discrete microcapsules in an encapsulatedelectrophoretic medium could be replaced by a continuous phase, thusproducing a so-called polymer-dispersed electrophoretic display(PDEPID), in which the electrophoretic medium comprises a plurality ofdiscrete droplets of an electrophoretic fluid and a continuous phase ofa polymeric material, and that the discrete droplets of electrophoreticfluid within such a polymer-dispersed electrophoretic display may beregarded as capsules or microcapsules even though no discrete capsulemembrane is associated with each individual droplet; see for example,the aforementioned U.S. Pat. No. 6,866,760. Accordingly, for purposes ofthe present application, such polymer-dispersed electrophoretic mediaare regarded as sub-species of encapsulated electrophoretic media.

A related type of electrophoretic display is a so-called “microcellelectrophoretic display”. In a microcell electrophoretic display, thecharged particles and the fluid are not encapsulated withinmicrocapsules but instead are retained within a plurality of cavitiesformed within a carrier medium, typically a polymeric film. See, forexample, U.S. Pat. Nos. 6,672,921 and 6,788,449, both assigned to SipixImaging, Inc.

Although electrophoretic media are often opaque (since, for example, inmany electrophoretic media, the particles substantially blocktransmission of visible light through the display) and operate in areflective mode, many electrophoretic displays can be made to operate ina so-called “shutter mode” in which one display state is substantiallyopaque and one is light-transmissive. See, for example, U.S. Pat. Nos.5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and6,184,856. Dielectrophoretic displays, which are similar toelectrophoretic displays but rely upon variations in electric fieldstrength, can operate in a similar mode; see U.S. Pat. No. 4,418,346.Other types of electro-optic displays may also be capable of operatingin shutter mode. Electro-optic media operating in shutter mode may beuseful in multi-layer structures for full color displays; in suchstructures, at least one layer adjacent the viewing surface of thedisplay operates in shutter mode to expose or conceal a second layermore distant from the viewing surface.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates.(Use of the word “printing” is intended to include all forms of printingand coating, including, but without limitation: pre-metered coatingssuch as patch die coating, slot or extrusion coating, slide or cascadecoating, curtain coating; roll coating such as knife over roll coating,forward and reverse roll coating; gravure coating; dip coating; spraycoating; meniscus coating; spin coating; brush coating; air knifecoating; silk screen printing processes; electrostatic printingprocesses; thermal printing processes; ink jet printing processes;electrophoretic deposition (See U.S. Pat. No. 7,339,715); and othersimilar techniques.) Thus, the resulting display can be flexible.Further, because the display medium can be printed (using a variety ofmethods), the display itself can be made inexpensively.

Other types of electro-optic media may also be used in the displays ofthe present invention. The bistable or multi-stable behavior ofparticle-based electrophoretic displays, and other electro-opticdisplays displaying similar behavior (such displays may hereinafter forconvenience be referred to as “impulse driven displays”), is in markedcontrast to that of conventional liquid crystal (“LC”) displays. Twistednematic liquid crystals are not bi- or multi-stable but act as voltagetransducers, so that applying a given electric field to a pixel of sucha display produces a specific gray level at the pixel, regardless of thegray level previously present at the pixel. Furthermore, LC displays areonly driven in one direction (from non-transmissive or “dark” totransmissive or “light”), the reverse transition from a lighter state toa darker one being affected by reducing or eliminating the electricfield. Finally, the gray level of a pixel of an LC display is notsensitive to the polarity of the electric field, only to its magnitude,and indeed for technical reasons commercial LC displays usually reversethe polarity of the driving field at frequent intervals. In contrast,bistable electro-optic displays act, to a first approximation, asimpulse transducers, so that the final state of a pixel depends not onlyupon the electric field applied and the time for which this field isapplied, but also upon the state of the pixel prior to the applicationof the electric field.

Whether or not the electro-optic medium used is bistable, to obtain ahigh-resolution display, individual pixels of a display must beaddressable without interference from adjacent pixels. One way toachieve this objective is to provide an array of non-linear elements,such as transistors or diodes, with at least one non-linear elementassociated with each pixel, to produce an “active matrix” display. Anaddressing or pixel electrode, which addresses one pixel, is connectedto an appropriate voltage source through the associated non-linearelement. Typically, when the non-linear element is a transistor, thepixel electrode is connected to the drain of the transistor, and thisarrangement will be assumed in the following description, although it isessentially arbitrary and the pixel electrode could be connected to thesource of the transistor. Conventionally, in high resolution arrays, thepixels are arranged in a two-dimensional array of rows and columns, suchthat any specific pixel is uniquely defined by the intersection of onespecified row and one specified column. The sources of all thetransistors in each column are connected to a single column electrode,while the gates of all the transistors in each row are connected to asingle row electrode; again the assignment of sources to rows and gatesto columns is conventional but essentially arbitrary, and could bereversed if desired. The row electrodes are connected to a row driver,which essentially ensures that at any given moment only one row isselected, i.e., that there is applied to the selected row electrode avoltage such as to ensure that all the transistors in the selected roware conductive, while there is applied to all other rows a voltage suchas to ensure that all the transistors in these non-selected rows remainnon-conductive. The column electrodes are connected to column drivers,which place upon the various column electrodes voltages selected todrive the pixels in the selected row to their desired optical states.(The aforementioned voltages are relative to a common front electrodewhich is conventionally provided on the opposed side of theelectro-optic medium from the non-linear array and extends across thewhole display.) After a pre-selected interval known as the “line addresstime” the selected row is deselected, the next row is selected, and thevoltages on the column drivers are changed so that the next line of thedisplay is written. This process is repeated so that the entire displayis written in a row-by-row manner

An adhesive layer may be used to join together layers of the display.For example, in some embodiments, the front plane electrode and/or thebackplane electrode are adhered to the electro-optic material layerusing an adhesive layer. As used herein, the electro-optic materiallayer also may be referred to as electro-optic medium, ink or ink layer.The adhesive may comprise a polymer (e.g., polyurethane) which may bethermally, chemically, and/or optically cured. As described furtherbelow, in some embodiments, the adhesive comprises a polyurethanecomprising select end-capping reagents which results in certainperformance enhancements. In some embodiments, the end-capping reagentcomprises a cyclic carbonate. In some embodiments, the end-cappingreagents comprise a first type of end-capping reagent and a second typeof end-capping reagent.

The use of adhesives comprises two or more cured moieties (formed by twoor more curing steps) may offer several advantages over traditionaladhesives. In some embodiments, improved rheology of the adhesive systemenables adhesive coatings on a layer (e.g., electro-optic layer such asan air-dried side that has a relatively rougher surface as compared tothe smooth, release side (“SSL”)) resulting in a decreased coat weight,decreased ink-adhesive coating thickness, improved display resolution,improved low temperature dynamic range, thinner coatings for flexibleapplications, and reduced formation of voids and/or defects as comparedto the use of adhesives with only one cured moiety. In certainembodiments, improved performance of an electro-optic assembly isobserved for embodiments where adhesive is dual-cured to form anelectro-optic assembly using as compared to being applied by hotmelting, including, but not limited to, reduced white state L* loss overtime, increased dynamic range, improved low temperature operation (e.g.,improved dynamic range), and increased volume resistivity. By contrast,traditional adhesives may suffer from poor low temperature performance,poor rheology, and may have electrical properties (e.g., resistivity)which reduces the functionality of the electro-optic material layer(e.g., reduced switching efficiency).

The term “cured moiety” as used herein generally refers to a physicalconnection (e.g., a covalent bond, a non-covalent bond, etc.) betweentwo or more polymer backbones. The term backbone is given its typicalmeaning in the art and generally refers to a series of covalently boundatoms that together create a continuous chain forming the polymer, andgenerally does not refer to any side chains (e.g., branches) orcross-linked groups. The cured moiety may comprise, in some cases, acrosslink (e.g., the reaction of two or more reactive functional groupswith a cros slinking reagent). In an exemplary embodiment, the curedmoiety is formed by the reaction of a reactive functional group, acuring species such as a crosslinking reagent, and a second reactivefunctional group, such that the first reactive functional group and thesecond reactive functional group are connected by the curing species. Incertain embodiments, the first reactive functional group and the secondreactive functional group are the same type of reactive functionalgroup. In some cases, the first reactive functional group and the secondreactive functional group may be different types of reactive functionalgroups. In some embodiments, the curing species is connected to thefirst reactive functional group and/or the second reactive functionalgroup via formation of a bond, such as an ionic bond, a covalent bond, ahydrogen bond, Van der Waals interactions, and the like. The covalentbond may be, for example, carbon-carbon, carbon-oxygen, oxygen-silicon,sulfur-sulfur, phosphorus-nitrogen, carbon-nitrogen, metal-oxygen, orother covalent bonds. The hydrogen bond may be, for example, betweenhydroxyl, amine, carboxyl, thiol, and/or similar functional groups.

In another exemplary embodiment, the cured moiety is formed by thethermoplastic drying of an adhesive material such that two or morepolymer backbones interact to form a bond (e.g., through intermolecularforces such as hydrogen bonding, dipole-dipole, etc.). For example, insome cases, an acrylic (e.g., polyacrylic) polymer may be dried (e.g.,via the application of heat to the adhesive material(s)) such that twoor more reactive functional groups on the polymer backbone undergothermoplastic reaction (e.g., by the removal of water and the increasein the glass transition temperature (Tg) of the adhesive material (e.g.,for an amorphous adhesive material) and the formation of a bond betweenthe two reactive functional groups) thereby forming a cured moietyconnecting the original polymer backbones.

In yet another embodiment, a polyurethane-acrylic hybrid adhesive iscured in a first step by thermoplastic drying, followed by curing inwhich crosslinking occurs between a reactive species on the polymerbackbone of the polyurethane with a reactive species on the acrylicbackbone.

In some embodiments, in which the adhesive is formed by two or morecuring steps, the adhesive comprises two or more types of curedmoieties. For example, in some embodiments, the adhesive comprises afirst type of cured moiety comprising a first crosslink (formed by thereaction of a first crosslinking reagent with two or more reactivespecies) and a second type of cured moiety comprising a second crosslink(formed by the reaction of a second crosslinking reagent with two ormore reactive species). The first and second crosslinking reagents maybe, in some cases, the same or different. In another embodiment, theadhesive may comprise a first type of cured moiety comprises a firstcrosslink and a second type of cured moiety comprising a thermoplasticlinkage.

The term “curing species” as used herein generally refers to a compoundthat facilitates the reaction between two or more reactive functionalgroups such that the reactive functional groups are connected. Thecuring species may be, in some cases, a crosslinking reagent. Thereaction of a curing species with two or more reactive functional groupsmay form a cured moiety, as described above.

As illustrated in FIG. 1A, in some embodiments, an electro-opticassembly 100 comprises a backplane electrode 110, a front planeelectrode 130, and an electro-optic material layer 120. As noted above,different layers of the assembly can be joined together with an adhesivelayer 140. In some embodiments, as shown in FIGS. 1A and 1B, backplaneelectrode 110 is adhered to the electro-optic material layer by adhesivelayer 140. In some embodiments, as illustrated in FIG. 1B, front planeelectrode 130 is adhered to electro-optic material layer 120 by adhesivelayer 142, which may comprise the same or different adhesive as adhesivelayer 140. As illustrated in FIG. 1C, an electro-optic material layer125 may comprise capsules 150 and a binder 160, described in more detailbelow. The capsules 150 may encapsulate one or more particles that canbe caused to move with the application of an electric field across theelectro-optic material layer 125. In some such embodiments, front planeelectrode 130 may be directly adjacent electro-optic material layer 125and backplane electrode 110 is adhered to the electro-optic materiallayer by adhesive layer 140. In an exemplary embodiment, as illustratedin FIG. 1D, backplane electrode 110 may be adhered to electro-opticmaterial layer 125 by adhesive layer 140 and front plane electrode 130may be adhered to electro-optic material layer 125 by adhesive layer142. In another exemplary embodiment, as illustrated in FIG. 1E, frontplane electrode 130 may be adhered to electro-optic material layer 125by adhesive layer 140 and backplane electrode 110 may be adhered toelectro-optic material layer 125 by adhesive layer 142.

It should be understood that the adhesive layer may be used to adhereany type and number of layers to one or more other layers in theassembly, and the assembly may include one or more additional layersthat are not shown in the figures. Additionally, while FIGS. 1C-1Eillustrate an encapsulated electro-optic medium, the adhesive layers areuseful in a variety of electro-optic assemblies, such as liquid crystal,frustrated internal reflection, and light-emitting diode assemblies.

In addition to the polyurethanes of the invention, the adhesive layersmay include additional components. Non-limiting examples of suitablecomponents include other polyurethanes, acrylics, alkyds, epoxies,aminos, and siloxanes. In some cases, the adhesive layer may comprisetwo or more types of similar adhesive materials (e.g., two types ofacrylics, an acrylic and an alkyd, a polyurethane and a siloxane, twotypes of polyurethanes, a polyurethane and an acrylic).

In some embodiments, the adhesive is provided in the form of adispersion (e.g., an aqueous dispersion). For example, in some cases, anadhesive dispersion may be used directly in a coating process and/or bysolutions of reactive monomers in dispersions or solutions of adhesivesto form an adhesive layer as described herein. In some cases, theaqueous dispersion comprises water which may be removed (e.g., via theapplication of heat) after deposition of the adhesive to one or moresurfaces.

Generally, polyurethanes are prepared via a polyadditional processinvolving a diisocyante. Non-limiting examples of polyurethanes includepolyether polyurethanes, polyester polyurethanes, polyether polyureas,polyureas, polyester polyureas, polyester polyureas, polyisocyanates(e.g., polyurethanes comprising isocyanate bonds), and polycarbodiimides(e.g., polyurethanes comprising carbodiimide bonds). Generally, however,the polyurethane contains urethane groups. The polyurethanes utilized inthe assemblies and methods described herein may be prepared usingmethods known in the art. Generally, an isocyanate-terminatedpolyurethane is formed by reaction of at least one diisocyanate compoundwith a secondary reagent comprising at least two groups which arecapable of reacting with an isocyanate group (e.g., a polyol). In someembodiments, the polyurethane is a linear polymer formed via reaction ofa diisocyanate compound and a secondary reagent comprising two groupswhich are capable of reacting with an isocyanate group (e.g., a diol).Following preparation of the isocyanate-terminated polyurethane, theterminal isocyanate groups may be deactivated via reaction with aterminating reagent, respectively, thereby forming a terminatedpolyurethane (e.g., such that the polyurethane and/or terminalisocyanate groups do not undergo further reaction). For example,following preparation of the isocyanate-terminated polyurethane, theterminal isocyanate groups may be end-capped via reaction with one ormore end-capping reagents, thereby forming an end-capped polyurethane.In some cases, the isocyanate-terminated polyurethane may be neutralizedvia reaction with a neutralizing reagent, such that the polyurethane maybe dispersed into water such as when stabilized by ionic groups. In someembodiments, the molecular weight of polyurethane may be controlled bythe addition of at least one type of end-capping reagent. End-cappingreagents are described in more detail below and may also be used in thepreparation of other adhesives. The polyurethane (e.g.,isocyanate-terminated polyurethane, end-capped polyurethane, and/orneutralized polyurethane) may also be optionally chain-extended viareaction with a chain-extending reagent. While the aforementioned stepsmay be conducted sequentially as described above, in alternativeembodiments, the order of the steps may be varied and/or one more stepsmay be carried out simultaneously. For example, in some embodiments, thepolyurethane may be formed by a providing a mixture of at least onediisocyanate, a secondary reagent comprising at least two groups whichare capable of reacting with an isocyanate group, and one or moreend-capping reagents, and substantially simultaneously reacting themixture. In some cases, the one or more end-capping reagents are addedafter reacting a mixture comprising at least one diisocyanate and asecond reagent comprising at least two groups which are capable ofreacting with an isocyanate group. The end-capping reagents may be addedduring the reaction of the mixture and/or after the reaction of themixture (e.g., after neutralization of the reaction, as describedherein).

In some embodiments, the isocyanate-terminated polyurethane is formedvia reaction of at least one diisocyanate compound with at least onedifunctional polyol or at least one multifunctional polyol. In someembodiments, the polyol is a diol (e.g., an oligomer with two alcoholterminal groups, a polymer with two alcohol terminal groups). Generally,the reaction is carried out using a stoichiometric excess of the atleast diisocyanate compound, thereby aiding in the formation of anisocyanate-terminated polyurethane. In some embodiments, the ratio ofthe at least one diisocyante compound to the diol is between about 2:1and about 1:2, or between about 1.5:1 and about 1:1.5, or about 1:1.Those of ordinary skill in the art will be able to adjust this ratiowhen using polyols which include more than two reactive —OH groups. Morethan one type of diisocyanate compound may be utilized, for example, twotypes, three types, or four types of diisocyanate compounds. Further,more than one type of diol (or polyol) may be utilized, for example, twotypes, three types, or four types of diols. In some embodiments, threetypes of diols are utilized.

The term diisocyanate is given its ordinary meaning in the art and isused to describe a linear, cyclic, or branch-chained hydrocarbons,including aromatic, cycloaliphatic, and aliphatic hydrocarbons havingtwo free isocyanate groups. Non-limiting examples of diisocyanatecompounds include 4,4-methylenebis(cyclohexylisocyanate) (H12MDI),α,α,α,α-tetramethylxylene diisocyanate,3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane isophoronediisocyanate and derivatives thereof, tetramethylene diisocyanate,hexamethylene diisocyanate (HDI) and derivatives thereof, 2,4-toluenediisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate,m-isopropenyl-α,α-dimethylbenzyl isocyanate, benzene1,3-bis(1-iscyanato-1-methylethyl, 1-5 naphthalene diisocyanate,phenylene diisocyanate, trans-cyclohexane-1,4-diisocyanate, bitolylenediisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl dimethylmethane diisocyanate, di- and tetraalkyl diphenyl methane diisocyanate,4,4′-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylenediisocyanate, the isomers of tolylene diisocyanate,1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethyl hexane,1-isocyanatomethyl-3-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane, chlorinated and brominated diisocyanates,phosphorus-containing diisocyanates, 4,4′-diisocyanatophenylperfluoroethane, tetramethoxy butane-1,4-diisocyanate,butane-1,4-diisocyanate, hexane-1,6-diisocyanate, dicyclohexyl methanediisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate,phthalic acid-bis-isocyanatoethyl ester, also polyisocyanates containingreactive halogen atoms, such as 1-chloromethylphenyl-2,4-diisocyanate,1-bromomethylphenyl-2,6-diisocyanate,3,3-bis-chloromethylether-4,4′-diphenyl diisocyanate. In someembodiments, the diisocyanate compound is4,4-methylenebis(cyclohexylisocyanate).

While most of the embodiments described herein utilize a secondaryreagent comprising a polyol or a diol, this is by no means limiting, andother types of secondary reagents may be utilized to form the adhesive(e.g., an adhesive comprising polyurethane). In some embodiments, thesecondary reagent comprises a polyamine or a diamine In certainembodiments, the secondary reagent comprises a thiol group. Thoseskilled in the art would be capable of selecting suitable secondaryreagents based upon the teachings of the specification. The term polyolis given its ordinary meaning in the art and refers to any organiccompound having two or more hydroxyl groups, wherein the hydroxyl groupsare capable of reacting with an isocyanate group. Generally, to formlinear polyurethanes, the polyol utilized is a diol. In someembodiments, the diol is a difunctional polyol. In certain embodiments,the diol is a difunctional oligomer with two reactive alcohol groups.Non-limiting examples of difunctional polyols include polyethyleneglycol, polypropylene glycol (PPO), polytetramethylene glycol. Themolecular weight of polyol may vary. In some embodiments, the molecularweight (Mn) is less than about 5000, or less than about 3000, or betweenabout 500 and about 5000, or between about 500 and about 4000, orbetween about 500 and about 3000.

In some embodiments, at least one diol comprises an ionic group (e.g., acarboxylic acid group). The ionic group may be used to stabilize thepolyurethane (e.g., when dispersed in water) and/or may be utilized forcrosslinking. Non-limiting examples of diols comprising an ionic groupinclude dimethylolpropionic acid (DMPA), dimethylolbutanoic acid,dimethylolpentanoic acid, diethylolpropionic acid, diethylolbutanoicacid, 1,4-dihydroxy-2-butane sulfonic acid, 1,5-dihydroxy-2-pentanesulfonic acid, 1,5-dihydroxy-3-pentane sulfonic acid,1,3-dihydroxy-2-propane sulfonic acid, dimethylolethane sulfonic acid,N-methyldiethanolamine, N-ethyidiethanolamine, N-propyidiethanolamine,N,N-dimethyl-2-dimethylolbutylamine, N,N-diethyl-2-dimethylolbutylamine,N,N-dimethyl-2-dimethylolpropylamine In some embodiments, the ionicgroup is a carboxylic acid group. Non-limiting examples of diolscomprises a carboxylic acid group include dimethylolpropionic acid,dimethylolbutanoic acid, dimethylolpentanoic acid, diethylolpropionicacid, and diethylolbutanoic acid, polyester diol, and other polymericcarboxylic acid groups. In some embodiments, the diol comprising anionic group is dimethylolpropionic acid.

As noted above, in some embodiments, the secondary reagent may comprisea first type of secondary reagent (e.g., a first type of diol) and asecond type of secondary reagent (e.g., a second type of diol). In someembodiments, the secondary reagent may comprise a first type ofsecondary reagent (e.g., a first type of diol), a second type ofsecondary reagent (e.g., a second type of diol), and a third type ofsecondary reagent (e.g., a third type of diol). In some embodiments, thefirst type of diol is a difunctional polyol (e.g., polypropyleneglycol), the second type of diol comprises an ionic group (e.g., acarboxylic acid group, such as DMPA), and the third type of diol mayfunction as a non-ionic stabilizer.

As noted above, while polyurethane is provided as an exemplary adhesivematerial, those skilled in the art would be capable of utilizing thecompositions and methods described herein in adhesives comprising othertypes of adhesives. In some embodiments, the adhesive comprises anacrylic. In certain embodiments, the adhesive comprises two or moretypes of adhesives (e.g., a polyurethane and an acrylic).

Such adhesive mixtures (i.e. hybrid adhesives) may be formed byphysically blending at least two components which may be any combinationof solution or dispersed materials in aqueous or solvent based media. Insome embodiments, the hybrid adhesives may also be formed by syntheticpolymerization processes where one component is polymerized in thepresence of a second polymeric component, or both polymers may be formedsimultaneously. In some cases, the hybrid adhesives may be formed byemulsifying polymerizable monomers in an adhesive dispersion that isused directly in the coating process, and/or by solutions of reactivemonomers in dispersions or solutions of adhesives. In some cases,polymerization of the monomers may occur at the primary or secondarystages (i.e. cures) and may also help in ink surface void filling andparticle coalescence (e.g., if using dispersions).

As described above, in some embodiments, the adhesive material comprisestwo or more reactive functional groups. The reactive functional groupsmay be positioned as end groups, along the backbone or along chainsextended from the backbone.

Reactive functional groups generally refer to a chemical group (presenton the adhesive) configured to react with one or more curing species(e.g., a crosslinking reagent, a chain-extending reagent). In someembodiments, the reactive functional group reacts with a curing speciesto form a cured moiety such as a crosslink, a thermoplastic linkage, abond between two types of adhesive materials, or the like. In certainembodiments, a reactive functional group may react with a curing speciessuch as a crosslinking reagent to form a crosslink. In some cases, areactive functional group may be configured to react with anotherreactive functional group under a particular set of conditions (e.g., ata particular range of temperatures). In some embodiments, a reactivefunctional group my react under certain conditions such that theadhesive material undergoes thermoplastic drying. Non-limiting examplesof reactive functional groups include hydroxyls, carbonyls, aldehydes,carboxylates, amines, imines, imides, azides, ethers, esters,sulfhydryls (thiols), silanes, nitriles, carbamates, imidazoles,pyrrolidones, carbonates, acrylates, alkenyls, and alkynyls. Otherreactive functional groups are also possible and those skilled in theart would be capable of selecting suitable reactive functional groupsfor use with dual cure adhesives, based upon the teachings of thisspecification. Those skilled in the art would also understand that thecuring steps described herein do not generally refer to the formation ofan adhesive material (e.g., polymerization of an adhesive backbone suchas a polyurethane backbone) but the further reaction of an adhesivematerial such that the adhesive material forms crosslinks, undergoesthermoplastic drying, or the like such that the adhesive undergoes asubstantial change in mechanical properties, viscosity, and/oradhesiveness. For example, in certain embodiments, one or more of theelastic modulus, the viscosity, and the adhesiveness of the adhesivematerial after curing may increase by between about 5% and about 1000%as compared to the elastic modulus, the viscosity, and/or theadhesiveness of the adhesive material prior to curing. In someembodiments, one or more of the elastic modulus, the viscosity, and theadhesiveness of the adhesive material after curing may increase by atleast about 10%, at least about 20%, at least about 50%, at least about100%, at least about 200%, or at least about 500% as compared to theelastic modulus, the viscosity, and/or the adhesiveness of the adhesivematerial prior to curing.

In some embodiments, the reactive functional group is present on thebackbone of the adhesive. For example, in embodiments where the adhesivecomprises a polyurethane, the reactive functional group may be presenton the diisocyante group and/or on the polyol group reacted to form thepolyurethane.

In certain embodiments, the reactive functional group is present on anend-capping reagent. As described above for the exemplaryisocyanate-terminated polyurethane adhesive, the isocyanate-terminatedpolyurethane may be end-capped by reaction with at least one type ofend-capping reagent, thereby forming an end-capped adhesive (e.g.,end-capped polyurethane). As noted above, use of an end-capping reagentmay aid in controlling the molecular weight of the adhesive. In someembodiments, more than one type of end-capping reagent may utilized, forexample, two types, three types, or four types of end-capping reagent.The total amount of end-capping agents may be adjusted to produce anadhesive which is either partially or completely end-capped.

For example, partial end-capping may be achieved by reaction of theadhesive (e.g., the isocyanate-terminated polyurethane) with less than a100% stoichiometric amount of the end-capping reagent(s). In someembodiments, following reaction of the isocyanate-terminatedpolyurethane with the end-capping reagent, 50 to 100% of thepolyurethane is end-capped. In certain embodiments, following reactionof the isocyanate-terminated polyurethane with the end-capping reagent,at least about 50%, at least about 60%, at least about 75%, at leastabout 80%, or at least about 90% of the polyurethane is terminated withan end-cap group. In some cases, less than or equal to 100%, less thanor equal to about 90%, less than or equal to about 80%, less than orequal to about 75%, or less than or equal to about 60% of thepolyurethane is terminated with an end-cap group. Combinations of theabove-referenced ranges are also possible (e.g., between about 50% and100%, between 50% and 75%, between 60% and 90%, between 75% and 100%).Those of ordinary skill in the art will be aware of methods to determinethe amount of isocyanate group remaining, for example, by determiningthe loss of isocyanates by IR and isocyanate titration and/or via gaschromatography-mass spectroscopy of residual end group monomers.End-capped adhesives such as polyurethanes may be neutralized and/orchain-extended, as described in more detail herein.

In certain embodiments, the end-capping reagent comprising the reactivefunctional group. Non-limiting examples of suitable end-capping reagents(e.g., comprising reactive functional groups) are shown in FIG. 2 andare described in more detail, below.

In some embodiments, at least one of the types of end-capping reagentincludes a compound having the structure as in Formula (I):

wherein R¹ is selected from the group consisting of hydrogen, optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted aryl, optionally substituted heteroaryl, optionallysubstituted nitrile, optionally substituted carbamate, optionallysubstituted imidazolium, optionally substituted pyrrolidone, optionallysubstituted carbonate, optionally substituted acrylate, optionallysubstituted ether, optionally substituted ester, optionally substitutedhalide, optionally substituted acid, optionally substituted silane,optionally substituted thiol, L is a linking group, optionally absent,and

represents the location of a bond to the polyurethane. Non-limitingexamples of linking groups include optionally substituted alkylenes,optionally substituted heteroalkylenes, optionally substituted arylenes,and optionally substituted heteroarylenes. In some embodiments, R¹ ishydrogen. In certain embodiments, R¹ comprises the reactive functionalgroup. In some embodiments, L comprises the reactive functional group.

In some embodiments, an end-capping reagent comprising Formula (I) isassociated with a polyurethane via reaction of a isocyanate-terminatedpolyurethane and an end-capping reagent comprising Formula (II):

Q-L-R¹   (II),

wherein L and R¹ are as described above in connection with Formula (I).In some embodiments, Q is hydroxyl (HO—) or amino (H₂N—) For example, insome such embodiments, the end-capping reagent is n-butanol.

Again, while polyurethane is used as an exemplary adhesive herein, thoseskilled in the art would be capable of utilizing any suitable adhesivewith one or more suitable end-capping reagents, as described herein.

In some embodiments, at least one of the types of end-capping reagentincludes a nitrile resulting in an end-capped polyurethane comprising anitrile. The term “nitrile” is given its ordinary meaning in the art andgenerally refers to a molecular group containing at least one type ofcyanide group. In some embodiments, the end-capping reagent comprising anitrile comprises Formula (III):

wherein L is described above as in Formula (I).

In some embodiments, Formula (III) comprises Formula (IV):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (III) or (IV) is associated witha polyurethane via reaction of a isocyanate-terminated polyurethane andan end-capping reagent comprising Formula (V):

Q-L-C≡N   (V)

wherein Q is hydroxyl or amino For example, in some such embodiments,the end-capping reagent is 3-hydroxypropionitrile.

In some embodiments, at least one of the types of end-capping reagentincludes a carbamate resulting in an end-capped polyurethane comprisinga carbamate. The term “carbamate” is given its ordinary meaning in theart and generally refers to a molecular group containing at least onetype of —OOCNH₂ group. In some embodiments, the end-capping reagentcomprising a carbamate comprises Formula (VI):

wherein L is described above as in Formula (I) and wherein each R² isthe same or different and is selected from the group consisting ofhydrogen, optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted aryl, optionally substitutedheteroaryl, optionally substituted halide, and optionally substitutedhydroxyl. In certain embodiments, R² comprises the reactive functionalgroup. In some embodiments, L comprises the reactive functional group.

In some embodiments, Formula (VI) comprises Formula (VII):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (VI) or (VII) is associated witha polyurethane via reaction of a isocyanate-terminated polyurethane andan end-capping reagent comprising Formula (VIII):

wherein Q is hydroxyl or amino, L is described above as in Formula (I),and R² is described above as in Formula (VI). For example, in some suchembodiments, the end-capping reagent is hydroxyethyl carbamate.

In some embodiments, at least one of the types of end-capping reagentincludes an imidazole resulting in an end-capped polyurethane comprisinga imidazole. In some embodiments, the end-capping reagent comprising aimidazole comprises Formula (IX):

wherein L is described above as in Formula (I) and R² is described aboveas in Formula (VI).

In some embodiments, Formula (IX) comprises Formula (X):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (IX) or (X) is associated with apolyurethane via reaction of a isocyanate-terminated polyurethane and anend-capping reagent comprising Formula (XI):

wherein Q is hydroxyl or amino and R² is described above as in Formula(VI). For example, in some such embodiments, the end-capping reagent is2-hydroxyethylmethyl imidazolium.

In some embodiments, at least one of the types of end-capping reagentincludes a cyclic carbonate resulting in an end-capped polyurethanecomprising an end-capping reagent comprising a cyclic carbonate. Theterm “cyclic carbonate” is given its ordinary meaning in the art andrefers to a molecular group containing at least one type of cycliccarbonate oligomer, e.g., dimer, trimer, tetramer, etc. In someembodiments, the end-capping reagent comprising a cyclic carbonatecomprises Formula (XII):

wherein R² is described above as in Formula (VI), L is described aboveas in Formula (I), n is 1-4, and

represents the location of a bond to the polyurethane. In someembodiments, R² is hydrogen. In some embodiments, n is 1. In certainembodiments, n is 2. In some embodiments, L is optionally substitutedalkylene. In some embodiments, Formula (XII) comprises Formula (XIII):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, R¹ ishydrogen. In some embodiments, an end-capping reagent comprising Formula(II) or (III) is associated with a polyurethane via reaction of aisocyanate-terminated polyurethane and an end-capping reagent comprisingFormula (XIV):

wherein L and R² are as described above in connection with Formula (XII)and Q is hydroxyl or amino. In some embodiments, the compound of Formula(XIV) comprises Formula (XV):

wherein m is as described above in connection with Formula (XIII). Insome embodiments, m is 1. For example, in some such embodiments, theend-capping reagent is glycerin carbonate.

In some embodiments, an end-capping reagent comprises a pyrrolidone. Insome embodiments, the end-capping reagent comprising a pyrrolidonecomprises Formula (XVI):

wherein each R² is the same or different and is selected from the groupconsisting of hydrogen, optionally substituted alkyl, optionallysubstituted heteroalkyl, optionally substituted aryl, optionallysubstituted heteroaryl, optionally substituted halide, and optionallysubstituted hydroxyl, M is a linking group, optionally absent, and —represents the location of a bond to the polyurethane. Non-limitedexamples of linking groups include optionally substituted alkylene andoptionally substituted heteroalkylene. In some embodiments, each R² ishydrogen. In some embodiments, M is optionally substituted alkylene. Insome embodiments, Formula (XVI) comprises Formula (XVII): In certainembodiments, M comprises the reactive functional group.

wherein r is 1-10. In some embodiments, r is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, r is 2. In some embodiments, anend-capping reagent comprising Formula (XVI) or (XVII) is associatedwith a polyurethane via reaction of a isocyanate-terminated polyurethaneand an end-capping reagent comprising Formula (XVIII):

wherein M and R² are as described above in connection with Formula (XVI)and Q is hydroxyl or amino. In some embodiments, the compound of Formula(XVIII) comprises Formula (XIX):

wherein r is as described above in connection with Formula (XVII). Insome embodiments, r is 2. For example, in some such embodiments, theend-capping reagent is 2-hydroxyethyl pyrrolidone.

In some embodiments, at least one of the types of end-capping reagentincludes an acrylate resulting in an end-capped polyurethane comprisingan acrylate. In some embodiments, the end-capping reagent comprising anacrylate comprises Formula (XX):

wherein L is described above as in Formula (I) and R² is described aboveas in Formula (VI).

In some embodiments, Formula (XX) comprises Formula (XXI):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (XX) or (XXI) is associated witha polyurethane via reaction of a isocyanate-terminated polyurethane andan end-capping reagent comprising Formula (XXII):

wherein Q is hydroxyl or amino and R² is described above as in Formula(VI). For example, in some such embodiments, the end-capping reagent is2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

In some embodiments, at least one of the types of end-capping reagentincludes an ether resulting in an end-capped polyurethane comprising anether. In some embodiments, the end-capping reagent comprising an ethercomprises Formula (XXIII):

wherein L is described above as in Formula (I) and R² is described aboveas in Formula (VI).

In some embodiments, Formula (XXIII) comprises Formula (XXIV):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (XXIII) or (XXIV) is associatedwith a polyurethane via reaction of a isocyanate-terminated polyurethaneand an end-capping reagent comprising Formula (XXV):

wherein Q is hydroxyl or amino and R² is described above as in Formula(VI). For example, in some such embodiments, the end-capping reagent is2-ethoxyethanol.

In some embodiments, at least one of the types of end-capping reagentincludes a halide resulting in an end-capped polyurethane comprising anhalide In some embodiments, the end-capping reagent comprising an halidecomprises Formula (XXVI):

wherein L is described above as in Formula (I), X is a halogen (e.g., F,Cl, Br, I), and Y is optionally substituted arylene, optionallysubstituted C₁₋₁₀ alkylene, or optionally substituted alkylene oxide. Insome embodiments, Y comprises the reactive functional group. In certainembodiments, X comprises the reactive functional group.

In some embodiments, Formula (XXVI) comprises Formula (XXVII):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (XXVI) or (XXVII) is associatedwith a polyurethane via reaction of a isocyanate-terminated polyurethaneand an end-capping reagent comprising Formula (XXVIII):

wherein Q is hydroxyl or amino For example, in some such embodiments,the end-capping reagent is 4-chlorobenzyl alcohol.

In some embodiments, Formula (XXVI) comprises Formula (XXVII):

wherein m is 1-10. In some embodiments, m is 1-5, or 1-3, or 1, or 2, or3, or 4, or 5. In some embodiments, m is 1. In some embodiments, anend-capping reagent comprising Formula (XXVI) or (XXVII) is associatedwith a polyurethane via reaction of a isocyanate-terminated polyurethaneand an end-capping reagent comprising Formula (XXVIII):

wherein Q is hydroxyl or amino For example, in some such embodiments,the end-capping reagent is 4-chlorobenzyl alcohol.

In some embodiments, at least one of the types of end-capping reagentincludes an acid resulting in an end-capped polyurethane comprising anacid. In some embodiments, the end-capping reagent comprising an acidcomprises Formula (XXIX) or Formula (XXX):

wherein L is described above as in Formula (I), A is sulfur phosphorous,or boron. In some such embodiments, L is -(CH₂)_(m)- and m is 1-10. Insome embodiments, m is 1-5, or 1-3, or 1, or 2, or 3, or 4, or 5. Insome embodiments, an end-capping reagent comprising Formula (XXIX) or(XXX) is associated with a polyurethane via reaction of aisocyanate-terminated polyurethane and an end-capping reagent comprisingFormula (XXXI) or Formula (XXXII):

wherein Q is hydroxyl or amino For example, in some such embodiments,the end-capping reagent is 3-aminopropane sulphonic acid.

Additional suitable end-capping reagents including an ether and/or anacid are described, for example, in U.S. Patent. Application Number US2011/0306724, which is incorporated herein by reference.

In some embodiments, at least one of the types of end-capping reagentincludes a silane resulting in an end-capped polyurethane comprising asilane. In some embodiments, the end-capping reagent comprising a silanecomprises Formula (XXXIII):

wherein L is described above as in Formula (I), and wherein each R³ isthe same or different and comprises —(CH₂)_(n)— or —O—(CH₂)_(n), whereeach n is the same or different and 1-4. In some embodiments, each n isthe same or different and is 1 or 2. In some embodiments, R³ comprisesthe reactive functional group.

In some embodiments, an end-capping reagent comprising Formula (XXXIII)is associated with a polyurethane via reaction of aisocyanate-terminated polyurethane and an end-capping reagent comprisingFormula (XXXIV):

wherein Q is hydroxyl or amino For example, in some such embodiments,the end-capping reagent is 3-aminopropyl.trimethoxysilane.

In some embodiments, a first type and a second type of end-cappingreagent are used. For example, in some cases, the first type ofend-capping reagent comprises a cyclic carbonate and the second type ofend-capping reagent comprises a pyrrolidone. Any suitable ratio of thefirst type of end-capping reagent to the second type of end-cappingreagent may be utilized, for example, between about 1:2 and about 2:1,between about 1:1.5 and about 1.5:1, or about 1:1.

Those of ordinary skill in the art will be aware of other suitable typesof end-capping reagents and/or reagents in addition to those describedherein. For example, in some embodiments, the end-capping group and/orreagent comprises an alkyl, an aryl, a cyano, a carbamate, and/or anacrylate group.

In some embodiments, the adhesive (e.g., end-capped orisocyanate-terminated polyurethane) may be chain extended via reactionof the adhesive with a chain-extending reagent. The chain extension maybe carried out under conditions suitable to obtain a targeted Mn of theadhesive and/or to obtain a targeted degree of functionality of theadhesive. In some embodiments, the chain extension may be carried outvia reaction of one or more of the side-groups of the adhesive. In someembodiments, the reactive functional group is present on thechain-extending reagent.

Those of ordinary skill in the art will be aware of methods and systemsfor determining the molecular weight of a polyurethane or other polymer(e.g., a polyol used to prepare the polyurethane). In some embodiments,the molecular weight may be determined using gel permeationchromatography (GPC). In some embodiments, the molecular weight (Mn) isdetermined using GPC calibrated using polystyrene standards.

Those of ordinary skill in the art will be aware of methods and systemsfor determining the degree of functionality (i.e. the average number permolecule and/or fraction of reactive functional group present in theadhesive capable of reacting with a curing species such that a curedmoiety such as a crosslink is formed).

Again, referring to polyurethane as an exemplary adhesive, in someembodiments, the chain-extending reagent may comprise a diol or adiamine For example, the chain-extending reagent can comprise a diaminocompound. Non-limiting examples of diamino compounds include compoundshaving the structure H₂N—R⁴—NH₂, wherein R⁴ is optionally substitutedarylene or optionally substituted alkylene. In some embodiments, R⁴ is—(CH₂)p- wherein p is 1-10, or 2-8, or 3-7, or 4-6. In some embodiments,the chain-extending reagent is hexamethylene diamine In certainembodiments, R⁴ comprises a reactive functional group. In an exemplaryembodiment, the chain-extending reagent is 1,3-diamino-2-propanol (e.g.,wherein the hydroxyl group is the reactive functional group).

In some embodiments, the chain-extending reagent comprises a diolcompound (e.g., as described above). Non-limiting examples of diolcompounds include compounds having the structure HO—R⁵—OH, wherein R⁵ isoptionally substituted arylene or optionally substituted alkylene. Insome embodiments, R⁵ is —(CH₂)p- wherein p is 1-10, or 2-8, or 3-7, or4-6. In certain embodiments, R⁵ comprises a reactive functional group.In an exemplary embodiment, the chain-extending reagent comprises thestructure as in Formula (XXXV):

wherein m is 1-100. In some embodiments, m is at least 1, at least 2, atleast 5, at least 10, at least 20, at least 50, or at least 75. Incertain embodiments, m is less than or equal to 100, less than or equalto 75, less than or equal to 50, less than or equal to 20, less than orequal to 10, less than or equal to 5, or less than or equal to 2.Combinations of the above-referenced ranges are also possible (e.g., mis 1 to 100, m is 1 to 20, m is 10 to 50, m is 20 to 75, m is 50 to100). Other ranges are also possible. Additional non-limiting examplesof chain-extending reagents (e.g., diaminos and diols) comprising one ormore functional groups are shown in FIG. 3.

In some embodiments, at least a portion of the remaining reactiveisocyanate groups following polymerization may be deactivated viaaddition of one or more terminating reagents such that the remainingisocyanate groups do not substantially react. For example, in someembodiments, the terminating reagent may be an end-capping reagent suchthat further reaction of the isocyanate group is terminated.

In certain embodiments, acid groups present on the polyurethane may beneutralized via addition of one or more neutralizing reagents such thatthe polyurethane may be dispersed into water. Non-limiting examples ofneutralizing reagent include hydoxides (e.g., potassium hydroxide,lithium hydroxide) and tertiary amines (e.g., triethylamine,tributylamine, ethyldipropylamine, ethyldibutylamine,diethylpropylamine, diethylmonobutylamine) In some embodiments, theneutralizing reagent is triethylamine Likewise, basic groups present onthe polyurethane may be neutralized via addition of one or more acidicneutralizing reagents such that the polyurethane may be dispersed intowater, such as acetic acid. The amount of neutralizing reagent utilizedmay be between about 10-150% (e.g., relative to the number of acidgroups present on the polyurethane). As described above, adhesives(e.g., as an aqueous dispersion, in an adhesive layer) described hereinare generally comprise two or more cured moieties formed via reaction(i.e. curing) of one or more reactive functional groups (e.g., with oneor more curing species). For example, in some embodiments, the adhesiveis formed via the reaction of at least one reactive functional group, atleast two reactive functional groups, at least three reactive functionalgroups, or at least four reactive functional groups. Each reactivefunctional group may be the same or different and is generally capableof reacting with one or more curing species, described in more detailbelow.

In some embodiments, the reactive functional group has a particulardipole moment. In some cases, the use of an adhesive formed via thereaction of one or more functional groups having a relatively highdipole moment (e.g., a dipole moment greater than 2 Debyes) may improveelectro-optical performance of an electro-optic display compared totraditional adhesives. Those skilled in the art would be capable ofselecting appropriate methods of determining the dipole moment of areactive group. The dipole moment of a functional group may rangebetween about 2 Debyes and about 6 Debyes. In some embodiments, thedipole moment of a functional group is at least about 2 Debyes, at leastabout 2.5 Debyes, at least about 3 Debyes, at least about 4 Debyes, orat least about 5 Debyes. For example, a cyclic carbonate group (e.g.,comprising a structure as in Formula (XIV)) may have a dipole moment ofabout 5 Debyes, a pyrrolidone (e.g., comprising a structure as inFormula (XVII)) may have a dipole moment of about 4 Debyes, a nitrile(e.g., comprising a structure as in Formula (V)) may have a dipolemoment of about 3.5 Debyes.

The reactive functional group is generally present in the adhesive in anamount ranging between about 5 mole % and about 25 mole % versus thetotal adhesive composition. In some embodiments, the reactive functionalgroup is present in the adhesive in an amount of at least about 5 mole%, at least about 10 mole %, at least about 15 mole %, or at least about20 mole %. In certain embodiments, the reactive functional group ispresent in the adhesive in an amount of less than or equal to about 25mole %, less than or equal to about 20 mole %, less than or equal toabout 15 mole %, or less than or equal to about 10 mole %. Combinationsof the above referenced ranges are also possible (e.g., between about 5mole % and about 25 mole %).

In some embodiments, the adhesive is cured by the reaction of at leastone reactive functional group with at least one curing species (e.g.,during curing of the adhesive). In an exemplary embodiment, the adhesiveis cured by the reaction of a first reactive functional group with afirst curing species (e.g., a first curing step to form a first curedmoiety) and a second reactive functional group with a second curingspecies (e.g., a second curing step to form a second cured moiety).Those skilled in the art would understand, based upon the teachings ofthis specification, that the reaction of at least one reactivefunctional group with at least one curing species is not intended toencompass the reaction (e.g., the reaction of a diisocyanate and asecondary reagent such as a diol that forms the polyurethane) whichforms the backbone of the adhesive prior to, for example, the additionof an end-capping reagent and/or a chain-extending reagent. That is tosay, the reaction of at least one reactive functional group with atleast one curing species as described herein generally takes placeduring curing of the adhesive (e.g., such that the adhesive undergoes achange in one of a mechanical property (e.g., increased Young's elasticmodulus), rheological property (e.g., increased viscosity), or thelike). However, one or more reactive functional groups may be present inthe backbone of the adhesive, as described above, and may react with oneor more curing species.

In some embodiments, the adhesive is cured by the reaction of a reactivefunctional group with a curing species such as a chain-extendingreagent, a crosslinking reagent, or combinations thereof. In certainembodiments, the adhesive is cured by the reaction of a first reactivefunctional group with a curing species such as a second reactivefunctional group which maybe present on the backbone or on anend-capping reagent. In an exemplary embodiment, the adhesive may becured by thermoplastic drying of the adhesive material such that two ormore reactive functional groups present on the adhesive material react.

In some cases, the curing species comprises a type of reactivefunctional group, as described above. For example, the curing speciesmay comprise a carboxylic acid group configured to react with a hydroxylreactive functional group present on the adhesive material backbone oron an end-capping reagent. In an exemplary embodiment, the reactivefunctional group comprises a carbon-carbon double bond or acarbon-carbon triple bond that reacts with a curing species such assulfhydryl via a thiolene reaction. In some embodiments, the reactivefunctional group is capable of reacting with a crosslinking reagent(i.e. crosslinker). That is to say, in some cases, the curing speciescomprises a crosslinker. Non-limiting examples of suitable crosslinkersinclude monomers, oligomers, and polymers comprising polyfunctionalreactive groups including amine, carbodiimide, epoxy, alcohol, thiol,isocyanate, or the like. Those skilled in the art would be capable ofselecting suitable crosslinkers based upon the teachings of thisspecification. In some embodiments, the curing species is achain-extending reagent, as described above. In certain embodiments, thereactive functional group is capable of self-crosslinking and/orself-chain extending such as a mono-, di,- or tri-alkoxysilane. In somesuch embodiments, the curing species may comprise the same type of groupas the reactive functional group (e.g., a silane) capable of reactingwith the reactive functional group.

In some embodiments, the adhesive is formed by the reaction of one ormore reactive functional groups present on the adhesive (e.g.,polyurethane) with two or more crosslinkers. For example, in certainembodiments, the adhesive is reacted with a first crosslinker (i.e. afirst cure) and a second crosslinker (i.e. a second cure). In someembodiments, the adhesive backbone is reacted with the first crosslinkerduring a first curing step such as drying and/or lamination of theadhesive. In certain embodiments, the adhesive is then reacted with thesecond crosslinker during a second curing step. In some embodiments, thefirst crosslinker and the second crosslinker have different rates ofcrosslinking with the adhesive (e.g., with one or more reactivefunctional groups on the adhesive backbone). In certain embodiments, thefirst crosslinker and the second crosslinker have similar rates ofcrosslinking with the reactive functional groups present on theadhesive. Advantageously, the use of two or more crosslinkers providesdesirable rheological properties to enable effective planarization ofthe adhesive during lamination and/or drying of the adhesive, and/or lowadhesive layer coat weight. In some embodiments, the mechanicalproperties of the adhesive can be controlled by the second crosslinker(i.e. during the second curing step). In some embodiments, the long termstress reliability of the adhesive can be controlled by the secondcrosslinker.

In some embodiments, the functional reactive group reacts with thecuring species in the presence of a stimulus such as electromagneticradiation (e.g., visible light, UV light, etc.), an electron beam,increased temperature (e.g., such as utilized during solvent extractionor condensation reactions), a chemical compound (e.g., thiolene), and/ora crosslinker. Exemplary embodiments of types of reactive functionalgroup reactions (e.g., curing steps) are shown in FIG. 4 includingdiamine or polyamine crosslinking, self-crosslinking, thiolene/UVcrosslinking, and UV crosslinking.

While the above description relates to an exemplary polyurethaneadhesive composition, incorporation of reactive functionality into othertypes of adhesive materials will be known to those skilled in the art.For example, epoxy functionality can be incorporated intopolyacrylate-based adhesives by use of epoxy containing acrylatemonomers, double-bond functionality can be incorporated in alkyd basedmaterials, etc. In some embodiments, as described above, the adhesivemay comprise two or more types of adhesive materials (i.e. an adhesivehybrid). For example, in some cases, the adhesive may comprise apolyacrylate such as acrylic (e.g., configured to undergo a first cureby a thermoplastic drying) and a polyurethane (e.g., configured toundergo a second cure via reaction of the polyurethane with a reactivefunctional group present on the acrylate).

As described above, in some embodiments, the adhesive layer ispositioned between the front plane electrode and the backplaneelectrode, which may apply the electric field needed to change theelectrical state of the electro-optic material. That is to say, theelectrical properties (e.g., resistivity, conductivity) of the adhesivemay change the electric field applied to the electro-optic material. Ifthe resistivity of the adhesive is too high, a substantial voltage dropmay occur within the adhesive layer, requiring an increase in voltageacross the electrodes. Increasing the voltage across the electrodes inthis manner is undesirable, since it may increase the power consumptionof the display, and may require the use of more complex and expensivecontrol circuitry to handle the increased voltage involved. By contrast,if the adhesive layer, which may extend continuously across theelectro-optic assembly, is in contact with a matrix of electrodes, as inan active matrix display, the volume resistivity of the adhesive shouldnot be too low, or lateral conduction of electric current through thecontinuous adhesive layer may cause undesirable cross-talk betweenadjacent electrodes. Furthermore, since the volume resistivity of mostmaterials may decrease rapidly with increasing temperature, if thevolume resistivity of the adhesive is too low, the performance of theassembly at temperatures substantially above room temperature isadversely affected. Accordingly, in some embodiments, the volumeresistivity of the adhesive may range between about 108 ohm·cm and about1012 ohm·cm, or between about 109 ohm·cm and about 1011 ohm·cm (e.g., atthe operating temperature of the assembly around 20° C.). Other rangesof volume resistivity are also possible.

The adhesive layer after curing (e.g., after a first cure and a secondcure) may have a particular average coat weight. For example, theadhesive layer can have an average coat weight ranging between about 2g/m² and about 25 g/m². In some embodiments, the adhesive layer has anaverage coat weight of at least about 2 g/m², at least about 4 g/m², atleast about 5 g/m², at least about 8 g/m², at least about 10 g/m², atleast about 15 g/m², or at least about 20 g/m². In certain embodiments,the adhesive layer has an average coat weight of less than or equal toabout 25 g/m², less than or equal to about 20 g/m², less than or equalto about 15 g/m², less than or equal to about 10 g/m², less than orequal to about 8 g/m², less than or equal to about 5 g/m², or less thanor equal to about 4 g/m². Combinations of the above-referenced rangesare also possible (e.g., between about 2 g/m² and about 25 g/m², betweenabout 4 g/m² and about 10 g/m², between about 5 g/m² and about 20 g/m²,between about 8 g/m² and about 25 g/m²). Other ranges are also possible.

The adhesive layer prior to curing may have a particular average wetcoat thickness (e.g., such that the adhesive does not significantlyalter electrical and/or optical properties of the electro-opticassembly). For example, the adhesive layer can have an average wet coatthickness ranging between about 1 microns and about 100 microns, betweenabout 1 microns and about 50 microns, or between about 5 microns and 25microns. In some embodiments, the adhesive layer may have an average wetcoat thickness of less than about 25 microns, less than about 20microns, less than about 15 microns, or less than about 12 microns, lessthan about 10 microns, or less than about 5 microns. In some embodiments(e.g., in embodiments where the adhesive is wet coated directed to anelectro-optic material), the adhesive layer may have an average wet coatthickness between about 1 micron and about 50 microns, or between about5 microns and 25 microns, or between about 5 microns and about 15microns. In some embodiments (e.g., in embodiments where the adhesive iscoated onto a layer and then laminated to an electro-optic material),the adhesive layer may have an average wet coat thickness between about15 microns and 30 microns, or 20 microns and 25 microns. Other wet coatthicknesses are also possible.

It should be understood that the adhesive layer may cover the entireunderlying layer, or the adhesive layer may only cover a portion of theunderlying layer.

Further, the adhesive layer may be applied as a laminate, which usuallycreates a thicker adhesive layer, or it may be applied as an overcoat,which usually creates a layer that is thinner than a laminate. Theovercoat layer may utilize a dual curing system where a first cureoccurs prior to overcoat such that the adhesive may be coated on theelectro-optic material surface (or another surface) and a second curesets the material after overcoating. The overcoat layer may be rough ifthe underlying surface is rough and only a thin layer is applied, or theovercoat layer may be used to planarize an underlying rough surface.Planarization may occur in a single step where the overcoat layer isapplied to planarize the rough surface, for example, adding sufficientadhesive to fill in any voids and smooth the surface and minimallyincrease the overall thickness. Alternatively, planarization may occurin two steps where the overcoat layer is applied to minimally coat therough surface and second coating is applied to planarize. In anotheralternative, the overcoat layer may be applied to a smooth surface.

Referring again to FIGS. 1C and 1D, in some embodiments, theelectro-optic assembly comprises electro-optic material layer 125,capsules 150, and binder 160. In certain embodiments, the binder mayalso be an adhesive, as described above. For example, the binder may bea polyurethane (e.g., comprising at least one type of end-group).

The electro-optic assembly of the present invention may constitute acomplete electro-optic display or only a sub-assembly of such a display(e.g., an electrophoretic display). Representative electrophoreticdisplays have been described, for example, in U.S. Pat. No. 7,012,735issued Mar. 14, 2006 which is hereby incorporated in its entirety byreference. A complete electro-optic display generally includes thepresence of at least one, and normally two, electrodes to produce theelectric field necessary to vary the optical state of the electro-opticmaterial, although in some cases only one of the two electrodes may be apermanent part of the display, with the other electrode being in theform a movable stylus or similar instrument which can be moved over thedisplay to write on the display. For example, in some embodiments, frontplane electrode 130 comprises an electrode. In certain embodiments,backplane electrode 110 comprises an electrode. In some cases, theelectrode may be light-transmissive. For example, the assembly may havethe form of an active matrix display, with the first layer comprising asingle continuous light-transmissive electrode extending across multiplepixels, and typically the whole, of the display.

In some embodiments, front plane electrode 130 and/or backplaneelectrode 110 comprises one or more electrode layers patterned to definethe pixels of the display. For example, one electrode layer may bepatterned into elongate row electrodes and a second electrode layer maybe patterned into elongate column electrodes running at right angles tothe row electrodes, the pixels being defined by the intersections of therow and column electrodes. Alternatively, in some embodiments, oneelectrode layer has the form of a single continuous electrode and asecond electrode layer is patterned into a matrix of pixel electrodes,each of which defines one pixel of the display. In another type ofelectro-optic display, which is intended for use with a stylus, printhead or similar movable electrode separate from the display, only one ofthe layers adjacent the electro-optic layer comprises an electrode, thelayer on the opposed side of the electro-optic layer typically being aprotective layer intended to prevent the movable electrode damaging theelectro-optic layer.

Referring again to FIGS. 1A-D, front plane electrode 130 may comprise apolymeric film or similar supporting layer (e.g., which may support therelatively thin light-transmissive electrode and protects the relativelyfragile electrode from mechanical damage) and backplane electrode 110comprises a support portion and a plurality of pixel electrodes (e.g.,which define the individual pixels of the display). In some cases, thebackplane electrode may further comprise non-linear devices (e.g., thinfilm transistors) and/or other circuitry used to produce on the pixelelectrodes the potentials needed to drive the display (e.g., to switchthe various pixels to the optical states necessary to provide a desiredimage on the display).

The electro-optic assembly may have the form of a front plane laminate.In such a front plane laminate, the front plane may comprise alight-transmissive electrically-conductive layer intended to form thefront electrode of a final display. The front plane may comprise apolymeric film or similar supporting layer (e.g., which supports therelatively thin electrically-conductive layer and protect it frommechanical damage). In some such embodiments, the electro-optic assemblymay include a release sheet, which is removed before the front planelaminate is laminated to the backplane electrode to form the finaldisplay.

In some embodiments, the electro-optic material layer comprises anencapsulated electrophoretic media. Referring again to FIGS. 1C and 1D,in some embodiments, electro-optic material layer 125 comprises capsules150 comprising encapsulated electrophoretic media and binder 160. Insome cases, the capsules may comprise encapsulated electrophoretic mediacomprising numerous small capsules, each of which itself comprises aninternal phase containing electrophoretically-mobile particles (e.g.,ink particles) suspended in a liquid suspending medium, and a capsulewall surrounding the internal phase. In some such embodiments, thecapsules are held within a polymeric binder (e.g., binder 160) to form acoherent layer positioned between two electrodes (e.g., in the frontplane electrode and the backplane electrode). In some cases, the wallssurrounding the discrete microcapsules in an encapsulatedelectrophoretic medium may be replaced by a continuous phase, thusproducing a so-called polymer-dispersed electrophoretic display, inwhich the electrophoretic medium comprises a plurality of discretedroplets of an electrophoretic fluid and a continuous phase of apolymeric material, and that the discrete droplets of electrophoreticfluid within such a polymer-dispersed electrophoretic display may beregarded as capsules or microcapsules even though no discrete capsulemembrane is associated with each individual droplet.

In some embodiments, the electrophoretic medium comprises a plurality ofcapsules, each of the capsules comprising a capsule wall, a suspendingfluid encapsulated within the capsule wall and a plurality ofelectrically-charged particles suspended in the suspending fluid andcapable of moving there through on application of an electric field tothe medium, the medium further comprising a binder surrounding thecapsules.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates. Useof the word “printing” is intended to include all forms of printing andcoating, including, but without limitation: pre-metered coatings such aspatch die coating, slot or extrusion coating, slide or cascade coating,curtain coating; roll coating such as knife over roll coating, forwardand reverse roll coating; gravure coating; dip coating; spray coating;meniscus coating; spin coating; brush coating; air knife coating; silkscreen printing processes; electrostatic printing processes; thermalprinting processes; ink jet printing processes; electrophoreticdeposition; and other similar techniques. Thus, in some cases, theresulting display may be flexible. Further, because the display mediumcan be printed (e.g., using a variety of methods), the display itselfcan be made inexpensively.

In some embodiments, the electro-optic display is a “microcellelectrophoretic display”. In a microcell electrophoretic display, thecharged particles and the fluid are not encapsulated withinmicrocapsules but instead may be retained within a plurality of cavitiesformed within a carrier medium (e.g., a polymeric film).

Although electrophoretic media are often opaque (e.g., in many types ofelectrophoretic media, the particles substantially block transmission ofvisible light through the display) and operate in a reflective mode,many electrophoretic displays can be made to operate in a so-called“shutter mode” in which one display state is substantially opaque andone is light-transmissive.

The adhesives described above may also be used in other electro-opticmaterials and electro-optic displays known in the art. For example, insome embodiments, the electro-optic material is a solid (e.g., a solidelectro-optic display). In some such embodiments, the electro-opticmaterial may comprise internal liquid- or gas-filled spaces. As such,the term “solid electro-optic displays” includes encapsulatedelectrophoretic displays, encapsulated liquid crystal displays, andother types of displays.

In some embodiments, the electro-optic display is a rotating bichromalmember (e.g., a rotating bichromal ball display. In some suchembodiments, the display uses a large number of small bodies (typicallyspherical or cylindrical) which have two or more sections with differingoptical characteristics, and an internal dipole. These bodies may besuspended within liquid-filled vacuoles within a matrix, the vacuolesbeing filled with liquid so that the bodies are free to rotate. Theappearance of the display may be changed by applying an electric fieldthereto, thus rotating the bodies to various positions and varying whichof the sections of the bodies is seen through a viewing surface. Thistype of electro-optic medium is typically bistable.

The term “bistable” is used herein in its conventional meaning in theart to refer to displays comprising display elements having first andsecond display states differing in at least one optical property, andsuch that after any given element has been driven, by means of anaddressing pulse of finite duration, to assume either its first orsecond display state, after the addressing pulse has terminated, thatstate may persist for at least several times, for example at least fourtimes, the minimum duration of the addressing pulse required to changethe state of the display element. In some cases, some particle-basedelectrophoretic displays capable of gray scale are stable not only intheir extreme black and white states but also in their intermediate graystates. This type of display is generally termed “multi-stable” ratherthan bistable, although for convenience the term “bistable” may be usedherein to cover both bistable and multi-stable displays.

Other electro-optic displays are known in the art and include anelectro-optic display using an electrochromic medium, for example anelectrochromic medium in the form of a nanochromic film comprising anelectrode formed at least in part from a semi-conducting metal oxide anda plurality of dye molecules capable of reversible color change attachedto the electrode; electro-wetting displays; and particle-basedelectrophoretic displays, in which a plurality of charged particles movethrough a suspending fluid under the influence of an electric field.

The adhesive layer may be formed using suitable techniques known in theart. In some embodiments, the adhesive layer is formed as a film andthen applied to the assembly, for example, via lamination. In suchembodiments, the adhesive (e.g., comprising an end-capped polyurethaneas described herein) may be coated onto a release layer or othersubstrate (e.g., a front or backplane electrode) and dried usingtechniques known in the art (e.g., via heating and/or exposure tovacuum). The substrate may comprise indium-tin-oxide (ITO) or a similarconductive coating (e.g., which acts as an electrode layer of the finaldisplay) on a plastic film or a release layer (e.g., comprising aflexible polymer). As a specific non-limiting example, the adhesivematerial may be dispensed (e.g., via use of a die or slot coater) on thesubstrate. The thickness of the material may be controlled byflowability or amount of material pumped per square area of material.Separately, a backplane electrode, containing an array of pixelelectrodes and an appropriate arrangement of conductors to connect thepixel electrodes to drive circuitry, may be prepared. To form the finaldisplay, the substrate having the capsule/binder layer thereon may belaminated (e.g., via application of heat and use of a roll laminator) tothe backplane electrode using an adhesive.

In an alternative embodiment, a similar process can be used to preparean electrophoretic display usable with a stylus or similar movableelectrode by replacing the backplane electrode with a simple protectivelayer, such as a plastic film, over which the stylus or other movableelectrode can slide. In some such embodiments, the backplane electrodeis itself flexible and is prepared by printing the pixel electrodes andconductors on a plastic film or other flexible substrate.

Those of ordinary skill in the art will be aware of suitable conditionsfor use in the synthetic methods described herein. For example, theadhesive material (e.g., the isocyanate-terminated polyurethane) may beprepared in a reactor wherein the reactants (e.g., diisocyante compoundand secondary reagent such as a diol) are combined, mixed, and reacted,either neat or in a solvent, wherein heat may be transferred in to, andaway from, the reactor. The synthesis of the adhesive may be conductedin an inert atmosphere (e.g., in the absence of water and in thepresence of an inert gas such as nitrogen and/or argon). The reactantsmay be added in any particular order. The adhesive may be reacted withone or more additional reagents (e.g., end-capping reagent(s),chain-extending reagent(s), neutralizing reagent(s)). In some cases,following a suitable period of time, a dispersing medium such as wateris added to the reaction mixture. Following synthesis of the adhesivematerial, the adhesive material may be dispersed in water (e.g., viaaddition of water to the reaction mixture or addition of the reactionmixture to water). In some embodiments, the adhesive (e.g., end-cappedand/or neutralized) may be chain-extended following dispersion in water.

The adhesive materials described herein can be cured. Curing mayinclude, but not be limited to, the reaction of one or more reactivefunctional groups with one or more curing species (e.g., such that theadhesive is crosslinked, extended, entangled, etc.) as described herein.In some cases, the adhesive may undergo two or more curing steps (e.g.,a first cure and a second cure). That is to say, the adhesive may becured by reacting a first reactive functional group with a first curingspecies (i.e. a first cure), and cured further by reacting a secondreactive functional group with a second curing species (i.e. a secondcure). In some embodiments, the adhesive layer is formed by curing theadhesive such that a first reactive functional group reacts with a firstcuring species and then, subsequently, curing the adhesive such that asecond reactive functional group reacts with a second curing species.The first and second cures may occur at substantially the same time ormay occur at substantially different times. The first reactivefunctional group may be the same or different as the second reactivefunctional group. The first curing species may be the same or differentas the second curing species.

The use of two or more cures (i.e. curing steps) may impart desirableproperties to an adhesive. For example, an adhesive having two or morecures may have low coat weights and/or thicknesses as compared to otheradhesives, may impart a desirable rheological property in the adhesive(e.g., after the first cure and/or after the second cure), and/or mayreduce or prevent the formation of voids and/or defects such that thereare substantially no voids and/or defects are present in the adhesivelayer after the first cure or after the second cure. The adhesive shouldgenerally have sufficient adhesive strength to bind the desired layer(s)to one another. In some cases, the adhesive has sufficient adhesivestrength to bind the desired layer(s) to one another after curing (e.g.,after the first cure, after the second cure). In some embodiments, theelectro-optic assembly is flexible and, therefore, the adhesive may havesufficient flexibility not to introduce defects into the assembly whenthe assembly is flexed.

Those skilled in the art would be capable of selecting suitable methodsfor measuring defects in an adhesive such as Orange Peel testing. Forexample, Orange Peel may be determined using a wave-scan instrument toilluminate the specimen at a 60° angle to the surface, and measure thereflected light intensity collected at the equal but opposite angle fromthe specimen surface.

The adhesive may have a particular average crossover temperature (Tc,e.g., measured as the temperature at which tan delta=1.0 at 1 Hz) beforeor after a cure. For example, in some embodiments, the adhesive has anaverage crossover temperature of between about 0° C. and about 80° C.before a first cure and/or before a second cure. In certain embodiments,the average crossover temperature of the adhesive is less than about 80°C., less than about 60° C., less than about 40° C., less than about 20°C., or less than about 10° C., before a first cure and/or before asecond cure. The average crossover temperature may increase after afirst cure (before a second cure) but remain between about 0° C. andabout 80° C. (e.g., between about 20° C. and about 80° C.). An adhesivewith an average crossover temperature as described above may flow and beeasily laminated to one or more layers (e.g., an electrode layer, arelease layer) and have substantially less defects as compared to anadhesive with a greater crossover temperature. Those skilled in the artwould understand that curing (e.g., crosslinking) the adhesive willgenerally increase the crossover temperature and that, for example, asecond cure may increase the crossover temperature to greater than 80°C. For example, in some embodiments, the average crossover temperatureof the adhesive after the second cure may be between about 80° C. andabout 250° C. In certain embodiments, the average crossover temperatureof the adhesive after the second cure is at least about 80° C., at leastabout 100° C., at least about 150° C., or at least about 200° C. In somecases, the average crossover temperature of the adhesive after thesecond cure is less than or equal to about 250° C., less than or equalto about 200° C., less than or equal to about 150° C., or less than orequal to about 100° C. Combinations of the above-referenced ranges arealso possible.

Adhesive material may be dispensed (for example, by means of a die orslot coater) over the electrophoretic layer or on a release layer. Inother embodiments, the adhesive may be directly coated (e.g., viasolution techniques) to the electro-optic material (or other underlyinglayer). The adhesive may then be dried using techniques known in the art(e.g., via heating and/or exposure to vacuum). Additional layers maythen be applied on the outer surface of the adhesive.

As a specific example, a dispersion comprising the adhesive material(e.g., a polyurethane dispersed in water) is dispensed (e.g., by meansof a die or slot coater) over an electro-optic material layer. Thethickness of the liquid material may be controlled, for example, via useof a doctor blade. In some embodiments, the upper surface of theelectro-optic material that the adhesive is being applied to may not beplanar. In such embodiments, the adhesive may be applied such that thefinal outer surface of the adhesive is planar or essentially planar.

In an exemplary embodiment, the adhesive material (e.g., comprising afirst type of reactive functional group and a second type of reactivefunctional group) may be coated on at least a portion of a first layer(e.g., indium-tin-oxide (ITO) or a similar conductive coating on aplastic film, a release layer, an electro-optic material layer) andcured (i.e. a first cure) such that the first type of reactivefunctional group reacts with a first type of curing species (e.g.,forming a first cured moiety). In some such embodiments, the adhesivemay be contacted with a second layer (e.g., indium-tin-oxide (ITO) or asimilar conductive coating on a plastic film, a release layer, anelectro-optic material layer) and cured (i.e. a second cure) such thatthe second type of reactive functional group reacts with a second typeof curing species (e.g., forming a second cured moiety). Those ofordinary skill in the art would understand that curing the adhesive(e.g., the first cure, the second cure) generally adheres the adhesivelayer to one or more layers. For example, the adhesive may adhere toonly one layer. In some cases, the adhesive adheres two layers together.In some cases, the one or more layers may be removed (e.g., a releaselayer) prior to the second curing and a third layer (e.g.,indium-tin-oxide (ITO) or a similar conductive coating on a plasticfilm, a release layer, an electro-optic material layer) may be contactedwith the adhesive (i.e. replacing the removed layer). In some suchembodiments, the removed layer may have facilitated decreasing theroughness of the adhesive, and/or protected the adhesive layer (e.g.,from physical damage, from contamination) prior to the second cure. Oneor more additional cures (e.g., a third cure, a fourth cure, etc.) mayalso be used. For example, in some cases, the adhesive comprises threeor more reactive functional groups that may be cured with three or morecuring steps.

The film of the adhesive on any substrate may be formed using techniquesknown in the art. For example, in some embodiments, the adhesive (e.g.,a polyurethane) is dispersed in water (or another solvent) and coatedonto a layer (e.g., indium-tin-oxide (ITO) or a similar conductivecoating on a plastic film, a release layer, an electro-optic materiallayer). Those of ordinary skill in the art will be aware of techniquesfor forming a solution coating on a surface, for example, spin coating,spray techniques, printed, die or slot coater, etc. Other additives maybe present in the solution. The solution coating may then be dried usingtechniques known in the art (e.g., heat and/or vacuum), thereby formingthe film.

The methods described herein may be carried out at any suitabletemperature. In some cases, each reaction (e.g., each curing stage) iscarried out at about room temperature (e.g., about 25° C., about 20° C.,between about 20° C. and about 25° C., or the like). In some cases,however, each reaction is carried out at temperatures below or aboveroom temperature. In some embodiments, each reaction is carried at atemperature between about 25° C. and about 140° C., about 25° C. andabout 75° C., or between about 50° C. and about 100° C.

In some embodiments, one or more of the reactions may be carried out inthe presence of a solvent. Alternatively, the reactions may be carriedout under neat conditions. Non-limiting examples of solvents includehydrocarbons (e.g., pentane, hexane, heptane), halocarbons (e.g.,chloroform, dichloromethane), ethers (e.g., diethylether,tetrahydrofuran (THF), 2-methoxyethyl ether (diglyme), and aromaticcompounds (e.g., benzene, toluene). As described herein, in someembodiments, a reaction may also be carried out in water.

For convenience, certain terms employed in the specification, examples,and appended claims are listed here. Definitions of specific functionalgroups and chemical terms are described in more detail below. Forpurposes of this invention, the chemical elements are identified inaccordance with the Periodic Table of the Elements, CAS version,Handbook of Chemistry and Physics, 75th Ed., inside cover, and specificfunctional groups are generally defined as described therein.Additionally, general principles of organic chemistry, as well asspecific functional moieties and reactivity, are described in OrganicChemistry, Thomas Sorrell, University Science Books, Sausalito: 1999.

The term “aliphatic,” as used herein, includes both saturated andunsaturated, nonaromatic, straight chain (i.e., unbranched), branched,acyclic, and cyclic (i.e., carbocyclic) hydrocarbons, which areoptionally substituted with one or more functional groups. As will beappreciated by one of ordinary skill in the art, “aliphatic” is intendedherein to include, but is not limited to, alkyl, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, and cycloalkynyl moieties. Thus, as usedherein, the term “alkyl” includes straight, branched and cyclic alkylgroups. An analogous convention applies to other generic terms such as“alkenyl”, “alkynyl”, and the like. Furthermore, as used herein, theterms “alkyl”, “alkenyl”, “alkynyl”, and the like encompass bothsubstituted and unsubstituted groups. In certain embodiments, as usedherein, “aliphatic” is used to indicate those aliphatic groups (cyclic,acyclic, substituted, unsubstituted, branched or unbranched) having 1-20carbon atoms. Aliphatic group substituents include, but are not limitedto, any of the substituents described herein, that result in theformation of a stable moiety (e.g., aliphatic, alkyl, alkenyl, alkynyl,heteroaliphatic, heterocyclic, aryl, heteroaryl, acyl, oxo, imino,thiooxo, cyano, isocyano, amino, azido, nitro, hydroxyl, thiol, halo,aliphaticamino, heteroaliphaticamino, alkylamino, heteroalkylamino,arylamino, heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy,heteroaliphaticoxy, alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy,aliphaticthioxy, heteroaliphaticthioxy, alkylthioxy, heteroalkylthioxy,arylthioxy, heteroarylthioxy, acyloxy, and the like, each of which mayor may not be further substituted).

As used herein, the term “alkyl” is given its ordinary meaning in theart and refers to the radical of saturated aliphatic groups, includingstraight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl(alicyclic) groups, alkyl substituted cycloalkyl groups, and cycloalkylsubstituted alkyl groups. In some cases, the alkyl group may be a loweralkyl group, i.e., an alkyl group having 1 to 10 carbon atoms (e.g.,methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, ordecyl). In some embodiments, a straight chain or branched chain alkylmay have 30 or fewer carbon atoms in its backbone, and, in some cases,20 or fewer. In some embodiments, a straight chain or branched chainalkyl may have 12 or fewer carbon atoms in its backbone (e.g., C₁-C₁₂for straight chain, C₃-C₁₂ for branched chain), 6 or fewer, or 4 orfewer. Likewise, cycloalkyls may have from 3-10 carbon atoms in theirring structure, or 5, 6 or 7 carbons in the ring structure. Examples ofalkyl groups include, but are not limited to, methyl, ethyl, propyl,isopropyl, cyclopropyl, butyl, isobutyl, t-butyl, cyclobutyl, hexyl, andcyclochexyl.

The term “alkylene” as used herein refers to a bivalent alkyl group. An“alkylene” group is a polymethylene group, i.e., —(CH₂)z-, wherein z isa positive integer, e.g., from 1 to 20, from 1 to 10, from 1 to 6, from1 to 4, from 1 to 3, from 1 to 2, or from 2 to 3. A substituted alkylenechain is a polymethylene group in which one or more methylene hydrogenatoms are replaced with a substituent. Suitable substituents includethose described herein for a substituted aliphatic group.

Generally, the suffix “-ene” is used to describe a bivalent group. Thus,any of the terms defined herein can be modified with the suffix “-ene”to describe a bivalent version of that moiety. For example, a bivalentcarbocycle is “carbocyclylene”, a bivalent aryl ring is “arylene”, abivalent benzene ring is “phenylene”, a bivalent heterocycle is“heterocyclylene”, a bivalent heteroaryl ring is “heteroarylene”, abivalent alkyl chain is “alkylene”, a bivalent alkenyl chain is“alkenylene”, a bivalent alkynyl chain is “alkynylene”, a bivalentheteroalkyl chain is “heteroalkylene”, a bivalent heteroalkenyl chain is“heteroalkenylene”, a bivalent heteroalkynyl chain is“heteroalkynylene”, and so forth.

The terms “alkenyl” and “alkynyl” are given their ordinary meaning inthe art and refer to unsaturated aliphatic groups analogous in lengthand possible substitution to the alkyls described above, but thatcontain at least one double or triple bond respectively.

In certain embodiments, the alkyl, alkenyl and alkynyl groups employedin the invention contain 1-20 aliphatic carbon atoms. In certain otherembodiments, the alkyl, alkenyl, and alkynyl groups employed in theinvention contain 1-10 aliphatic carbon atoms. In yet other embodiments,the alkyl, alkenyl, and alkynyl groups employed in the invention contain1-8 aliphatic carbon atoms. In still other embodiments, the alkyl,alkenyl, and alkynyl groups employed in the invention contain 1-6aliphatic carbon atoms. In yet other embodiments, the alkyl, alkenyl,and alkynyl groups employed in the invention contain 1-4 carbon atoms.Illustrative aliphatic groups thus include, but are not limited to, forexample, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl,isobutyl, t-butyl, n-pentyl, sec-pentyl, isopentyl, t-pentyl, n-hexyl,sec-hexyl, moieties and the like, which again, may bear one or moresubstituents. Alkenyl groups include, but are not limited to, forexample, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, and thelike. Representative alkynyl groups include, but are not limited to,ethynyl, 2-propynyl (propargyl), 1-propynyl and the like.

The term “cycloalkyl,” as used herein, refers specifically to groupshaving three to ten, preferably three to seven carbon atoms. Suitablecycloalkyls include, but are not limited to cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl and the like, which, as in the caseof other aliphatic, heteroaliphatic, or heterocyclic moieties, mayoptionally be substituted with substituents including, but not limitedto aliphatic; heteroaliphatic; aryl; heteroaryl; arylalkyl;heteroarylalkyl; alkoxy; aryloxy; heteroalkoxy; heteroaryloxy;alkylthio; arylthio; heteroalkylthio; heteroarylthio; —F; —Cl; —Br; —I;—OH; —NO2; —CN; —CF₃; —CH₂CF_(3;) —CHCl₂; —CH₂OH; —CH₂CH₂OH; —CH₂NH₂;—CH₂SO₂CH₃; —C(O)Rx; —CO₂(Rx); —CON(Rx)₂; —OC(O)Rx; —OCO2Rx; —OCON(Rx)₂;—N(Rx)₂; —S(O)₂Rx; —NRx(CO)Rx, wherein each occurrence of Rxindependently includes, but is not limited to, aliphatic,heteroaliphatic, aryl, heteroaryl, arylalkyl, or heteroarylalkyl,wherein any of the aliphatic, heteroaliphatic, arylalkyl, orheteroarylalkyl substituents described above and herein may besubstituted or unsubstituted, branched or unbranched, cyclic or acyclic,and wherein any of the aryl or heteroaryl substituents described aboveand herein may be substituted or unsubstituted. Additional examples ofgenerally applicable substituents are illustrated by the specificembodiments shown in the Examples that are described herein.

The term “heteroaliphatic,” as used herein, refers to an aliphaticmoiety, as defined herein, which includes both saturated andunsaturated, nonaromatic, straight chain (i.e., unbranched), branched,acyclic, cyclic (i.e., heterocyclic), or polycyclic hydrocarbons, whichare optionally substituted with one or more functional groups, and thatcontain one or more oxygen, sulfur, nitrogen, phosphorus, or siliconatoms, e.g., in place of carbon atoms. In certain embodiments,heteroaliphatic moieties are substituted by independent replacement ofone or more of the hydrogen atoms thereon with one or more substituents.As will be appreciated by one of ordinary skill in the art,“heteroaliphatic” is intended herein to include, but is not limited to,heteroalkyl, heteroalkenyl, heteroalkynyl, heterocycloalkyl,heterocycloalkenyl, and heterocycloalkynyl moieties. Thus, the term“heteroaliphatic” includes the terms “heteroalkyl,” “heteroalkenyl”,“heteroalkynyl”, and the like. Furthermore, as used herein, the terms“heteroalkyl”, “heteroalkenyl”, “heteroalkynyl”, and the like encompassboth substituted and unsubstituted groups. In certain embodiments, asused herein, “heteroaliphatic” is used to indicate those heteroaliphaticgroups (cyclic, acyclic, substituted, unsubstituted, branched orunbranched) having 1-20 carbon atoms. Heteroaliphatic group substituentsinclude, but are not limited to, any of the substituents describedherein, that result in the formation of a stable moiety (e.g.,aliphatic, alkyl, alkenyl, alkynyl, heteroaliphatic, heterocyclic, aryl,heteroaryl, acyl, sulfinyl, sulfonyl, oxo, imino, thiooxo, cyano,isocyano, amino, azido, nitro, hydroxyl, thiol, halo, aliphaticamino,heteroaliphaticamino, alkylamino, heteroalkylamino, arylamino,heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy, heteroaliphaticoxy,alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy, aliphaticthioxy,heteroaliphaticthioxy, alkylthioxy, heteroalkylthioxy, arylthioxy,heteroarylthioxy, acyloxy, and the like, each of which may or may not befurther substituted).

The term “heteroalkyl” is given its ordinary meaning in the art andrefers to an alkyl group as described herein in which one or more carbonatoms is replaced by a heteroatom. Suitable heteroatoms include oxygen,sulfur, nitrogen, phosphorus, and the like. Examples of heteroalkylgroups include, but are not limited to, alkoxy, amino, thioester,poly(ethylene glycol), and alkyl-substituted amino.

The terms “heteroalkenyl” and “heteroalkynyl” are given their ordinarymeaning in the art and refer to unsaturated aliphatic groups analogousin length and possible substitution to the heteroalkyls described above,but that contain at least one double or triple bond respectively.

Some examples of substituents of the above-described aliphatic (andother) moieties of compounds of the invention include, but are notlimited to aliphatic; heteroaliphatic; aryl; heteroaryl; alkylaryl;alkylheteroaryl; alkoxy; aryloxy; heteroalkoxy; heteroaryloxy;alkylthio; arylthio; heteroalkylthio; heteroarylthio; F; Cl; Br; I; —OH;—NO₂; —CN; —CF3; —CHF₂; —CH₂F; —CH₂CF₃; —CHCl₂; —CH₂OH; —CH₂CH₂OH;—CH₂NH₂; —CH₂SO₂CH₃; —C(O)Rx; —CO₂(Rx); —CON(Rx)₂; —OC(O)Rx; —OCO2Rx;—OCON(Rx)₂; —N(Rx)₂; —S(O)₂Rx; —NRx(CO)Rx wherein each occurrence of Rxindependently includes, but is not limited to, aliphatic, alycyclic,heteroaliphatic, heterocyclic, aryl, heteroaryl, alkylaryl, oralkylheteroaryl, wherein any of the aliphatic, heteroaliphatic,alkylaryl, or alkylheteroaryl substituents described above and hereinmay be substituted or unsubstituted, branched or unbranched, cyclic oracyclic, and wherein any of the aryl or heteroaryl substituentsdescribed above and herein may be substituted or unsubstituted.Additional examples of generally applicable substituents are illustratedby the specific embodiments shown in the Examples that are describedherein.

The term “aryl” is given its ordinary meaning in the art and refers toaromatic carbocyclic groups, optionally substituted, having a singlering (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fusedrings in which at least one is aromatic (e.g.,1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is,at least one ring may have a conjugated pi electron system, while other,adjoining rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, arylsand/or heterocyclyls. The aryl group may be optionally substituted, asdescribed herein. Substituents include, but are not limited to, any ofthe previously mentioned substituents, i.e., the substituents recitedfor aliphatic moieties, or for other moieties as disclosed herein,resulting in the formation of a stable compound. In some cases, an arylgroup is a stable mono- or polycyclic unsaturated moiety havingpreferably 3-14 carbon atoms, each of which may be substituted orunsubstituted. “Carbocyclic aryl groups” refer to aryl groups whereinthe ring atoms on the aromatic ring are carbon atoms. Carbocyclic arylgroups include monocyclic carbocyclic aryl groups and polycyclic orfused compounds (e.g., two or more adjacent ring atoms are common to twoadjoining rings) such as naphthyl groups.

The terms “heteroaryl” is given its ordinary meaning in the art andrefers to aryl groups comprising at least one heteroatom as a ring atom.A “heteroaryl” is a stable heterocyclic or polyheterocyclic unsaturatedmoiety having preferably 3-14 carbon atoms, each of which may besubstituted or unsubstituted. Substituents include, but are not limitedto, any of the previously mentioned substituents, i.e., the substituentsrecited for aliphatic moieties, or for other moieties as disclosedherein, resulting in the formation of a stable compound. In some cases,a heteroaryl is a cyclic aromatic radical having from five to ten ringatoms of which one ring atom is selected from S, O, and N; zero, one, ortwo ring atoms are additional heteroatoms independently selected from S,O, and N; and the remaining ring atoms are carbon, the radical beingjoined to the rest of the molecule via any of the ring atoms, such as,for example, pyridyl, pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl,imidazolyl, thiazolyl, oxazolyl, isooxazolyl, thiadiazolyl,oxadiazolyl,thiophenyl, furanyl, quinolinyl, isoquinolinyl, and the like.

It will also be appreciated that aryl and heteroaryl moieties, asdefined herein may be attached via an alkyl or heteroalkyl moiety andthus also include -(alkyl)aryl, -(heteroalkyl)aryl,-(heteroalkyl)heteroaryl, and -(heteroalkyl)heteroaryl moieties. Thus,as used herein, the phrases “aryl or heteroaryl moieties” and “aryl,heteroaryl, -(alkyl)aryl, -(heteroalkyl)aryl, -(heteroalkyl)heteroaryl,and -(heteroalkyl)heteroaryl” are interchangeable. Substituents include,but are not limited to, any of the previously mentioned substituents,i.e., the substituents recited for aliphatic moieties, or for othermoieties as disclosed herein, resulting in the formation of a stablecompound.

It will be appreciated that aryl and heteroaryl groups (includingbicyclic aryl groups) can be unsubstituted or substituted, whereinsubstitution includes replacement of one or more of the hydrogen atomsthereon independently with any one or more of the following moietiesincluding, but not limited to: aliphatic; alicyclic; heteroaliphatic;heterocyclic; aromatic; heteroaromatic; aryl; heteroaryl; alkylaryl;heteroalkylaryl; alkylheteroaryl; heteroalkylheteroaryl; alkoxy;aryloxy; heteroalkoxy; heteroaryloxy; alkylthio; arylthio;heteroalkylthio; heteroarylthio; F; Cl; Br; I; —OH; —NO₂; —CN; —CF₃;—CHF₂; —CH₂F; —CH₂CF₃; —CHCl₂; —CH₂OH; —CH₂CH₂OH; —CH₂NH₂; —CH₂SO₂CH3;—C(O)Rx; —CO₂(Rx); —CON(Rx)₂; —OC(O)Rx; —OCO₂Rx; —OCON(Rx)₂; —N(Rx)₂;—S(O)₂Rx; —NRx(CO)Rx wherein each occurrence of Rx independentlyincludes, but is not limited to, aliphatic, alicyclic, heteroaliphatic,heterocyclic, aromatic, heteroaromatic, aryl, heteroaryl, alkylaryl,alkylheteroaryl, heteroalkylaryl or heteroalkylheteroaryl, wherein anyof the aliphatic, alicyclic, heteroaliphatic, heterocyclic, alkylaryl,or alkylheteroaryl substituents described above and herein may besubstituted or unsubstituted, branched or unbranched, saturated orunsaturated, and wherein any of the aromatic, heteroaromatic, aryl,heteroaryl, -(alkyl)aryl or -(alkyl)heteroaryl substituents describedabove and herein may be substituted or unsubstituted. Additionally, itwill be appreciated, that any two adjacent groups taken together mayrepresent a 4, 5, 6, or 7-membered substituted or unsubstitutedalicyclic or heterocyclic moiety. Additional examples of generallyapplicable substituents are illustrated by the specific embodimentsdescribed herein.

The terms “halo” and “halogen” as used herein refer to an atom selectedfrom the group consisting of fluorine, chlorine, bromine, and iodine.

It will be appreciated that the above groups and/or compounds, asdescribed herein, may be optionally substituted with any number ofsubstituents or functional moieties. That is, any of the above groupsmay be optionally substituted. As used herein, the term “substituted” iscontemplated to include all permissible substituents of organiccompounds, “permissible” being in the context of the chemical rules ofvalence known to those of ordinary skill in the art. In general, theterm “substituted” whether preceded by the term “optionally” or not, andsubstituents contained in formulas of this invention, refer to thereplacement of hydrogen radicals in a given structure with the radicalof a specified substituent. When more than one position in any givenstructure may be substituted with more than one substituent selectedfrom a specified group, the substituent may be either the same ordifferent at every position. It will be understood that “substituted”also includes that the substitution results in a stable compound, e.g.,which does not spontaneously undergo transformation such as byrearrangement, cyclization, elimination, etc. In some cases,“substituted” may generally refer to replacement of a hydrogen with asubstituent as described herein. However, “substituted,” as used herein,does not encompass replacement and/or alteration of a key functionalgroup by which a molecule is identified, e.g., such that the“substituted” functional group becomes, through substitution, adifferent functional group. For example, a “substituted phenyl group”must still comprise the phenyl moiety and cannot be modified bysubstitution, in this definition, to become, e.g., a pyridine ring. In abroad aspect, the permissible substituents include acyclic and cyclic,branched and unbranched, carbocyclic and heterocyclic, aromatic andnonaromatic substituents of organic compounds. Illustrative substituentsinclude, for example, those described herein. The permissiblesubstituents can be one or more and the same or different forappropriate organic compounds. For purposes of this invention, theheteroatoms such as nitrogen may have hydrogen substituents and/or anypermissible substituents of organic compounds described herein whichsatisfy the valences of the heteroatoms. Furthermore, this invention isnot intended to be limited in any manner by the permissible substituentsof organic compounds.

Examples of substituents include, but are not limited to, halogen,azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl,amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate,carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido,ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromaticmoieties, —CF₃, —CN, aryl, aryloxy, perhaloalkoxy, aralkoxy, heteroaryl,heteroaryloxy, heteroarylalkyl, heteroaralkoxy, azido, amino, halide,alkylthio, oxo, acylalkyl, carboxy esters, carboxamido, acyloxy,aminoalkyl, alkylaminoaryl, alkylaryl, alkylaminoalkyl, alkoxyaryl,arylamino, aralkylamino, alkylsulfonyl, carboxamidoalkylaryl,carboxamidoaryl, hydroxyalkyl, haloalkyl, alkylaminoalkylcarboxy,aminocarboxamidoalkyl, cyano, alkoxyalkyl, perhaloalkyl,arylalkyloxyalkyl, and the like.

These and other aspects of the present invention will be furtherappreciated upon consideration of the following Examples, which areintended to illustrate certain particular embodiments of the inventionbut are not intended to limit its scope, as defined by the claims.

EXAMPLES Example 1 Synthesis of a Polyurethane Dispersion with ChainExtension Using a Non-Stoichiometric Amount of End Group Monomer, LowerSolvent Content, Catalyzed with Chain Extension After Dispersion—withGlycerin Carbonate (CCARB) End Group (EG) (Adhesive A)

To a 1 1, 3-necked flask was added 24.50 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI), 3.29 g ofDMPA (dimethylolpropionic acid), 70.80 g poly(propylene glycol)(Mn-2,000) and 7.58 g YmerN120 under a nitrogen atmosphere. 0.057 g ofdibutyltin dilaurate was then added and the mixture was heated to 68-71°C. After 5.5 hours, 4.61 g of glycerin carbonate was added to thereaction mixture with stirring for an additional 2 hours at which time1.44 g N-Methyl-2-pyrrolidone (NMP) was added to lower the viscosity.After an additional 1 hour, triethylamine (2.28 g) was added withstirring for 15 minutes, at which time the prepolymer was dispersed into167 g deionized water (DIW) at 39° C. The prepolymer was added over 15minutes. A solution of HMDA (0.631 g) in DIW (10.3 g) was added dropwiseto the dispersion over 12 minutes. After an additional 60 minutes aclear, slightly opaque dispersion was isolated.

Example 2 Synthesis of a Polyurethane Dispersion Using a Mixture of EndGroup Monomers, Catalyzed, with Chain Extension AfterDispersion—Glycerin Carbonate/3-Aminopropyl Trimethoxysilane (AdhesiveB)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 76.12 gpoly(propylene glycol) (Mn-2,000), 8.806 g of Ymer N120 (Perstorp), and4.193 g of DMPA (dimethylolpropionic acid). 28.6 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 0.060 gof dibutyltin dilaurate was added and the mixture was heated to 75-76°C. for 3.5 hours. Glycerin carbonate (2.946 g) was added and thereaction was heated for an additional 3 hours. TEA (3.71 g) was addedand after 15 minutes, the prepolymer was dispersed into 202 g DIW at˜39° C. over 10 minutes. After an additional 5 minutes mixing at 1000rpm, HMDA (2.09 g) in DIW (15.0 g) and 3-aminopropyl trimethoxysilane(2.216 g) were separately added dropwise to the dispersion over 10minutes. After an additional 60 minutes a clear, translucent dispersionwas isolated.

Example 3 Synthesis of a Polyurethane Dispersion Using a Mixture of EndGroup monomers, Catalyzed, with Chain Extension AfterDispersion—Glycerin Carbonate/3-Aminopropyl Trimethoxysilane (AdhesiveC)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 65.56 gpoly(propylene glycol) (Mn-2,000), 7.866 g of Ymer N120 (Perstorp), and3.611 g of DMPA (dimethylolpropionic acid). 24.7 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 0.049 gof dibutyltin dilaurate was added and the mixture was heated to 75-76°C. for 3.5 hours. Glycerin carbonate (1.586 g) was added and thereaction was heated for an additional 2.5 hours. TEA (3.03 g) was addedand after 15 minutes, the prepolymer was dispersed into 175 g DIW at˜39° C. over 15 minutes. After an additional 5 minutes mixing at 900rpm, HMDA (1.26 g) in DIW (15.3 g) and 3-aminopropyl trimethoxysilane(3.13 g) were separately added dropwise to the dispersion over 20minutes. After an additional 100 minutes a clear, translucent dispersionwas isolated.

Example 4 Synthesis of a Polyurethane Dispersion Without Chain ExtensionUsing a Stoichiometric Amount of End Group Monomer, in Solvent andCatalyzed, Stepwise Addition of Reagents—Glycerin Carbonate (Adhesive D)

To a 1 1, 3-necked flask was added 33.20 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 91.70 gpoly(propylene glycol) (Mn-2,000) under a nitrogen atmosphere. 0.097 gof dibutyltin dilaurate was added and the mixture was heated to 68-70°C. After 4.5 hours, 18.36 g of a mix of 6.985 g of DMPA(dimethylolpropionic acid) and 14.75 g NMP was added directly to thereactor with stirring for an additional 1.5 hours, after which thereactor was cooled and stirring discontinued overnight. The followingday, the mix was reheated to 75-77° C. for 5 hours, followed by additionof 8.704 g glycerin carbonate. After an additional 3 hours, heating andstirring were terminated.

114.7 g of the above prepolymer mix was transferred to a second reactorand heated to 70° C. 2.7 g of TEA (triethylamine) was added and stirredfor 45 minutes, after which the prepolymer was dispersed into 163.5 gDIW at 45° C. over 30 minutes. After an additional 30 minutes thesemi-translucent dispersion was isolated.

Example 5 Synthesis of a Polyurethane Dispersion Without Chain ExtensionUsing a Stoichiometric Amount of End Group Monomer—Catalyzed, InverseAddition of DIW—Glycerin Carbonate (Adhesive E)

To a 500 ml, 3-necked flask was added 35.76 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI), 6.31 g ofDMPA (dimethylolpropionic acid) and 98.36 g poly(propylene glycol)(Mn-2,000) under a nitrogen atmosphere. 0.076 g of dibutyltin dilauratewas added and the mixture was heated first to 72° C. for 2 hours then to80° C. for 4 hours. 9.33 g of glycerin carbonate was added and heatedfor 1.5 hours after which heating and stirring were terminated. After 15hours, the mix was reheated to 70-75° C. for 1.5 hours, followed byaddition of 3.54 g of TEA (triethylamine). After 45 minutes of mixing266.0 g of DIW was added over 45 minutes with mixing at 750 rpm withcooling to 38-40° C. The milky-white dispersion was mixed for anadditional 1.5 hours and subsequently isolated.

Example 6 Synthesis of a Polyurethane Dispersion with Chain ExtensionAfter Dispersion Using a Non-Stoichiometric Amount of End Group Monomerin Solvent, Catalyzed—Glycerin Carbonate EG (Adhesive F)

To a 1 1, 3-necked flask was added 31.82 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI), 5.79 g ofDMPA (dimethylolpropionic acid), 87.20 g poly(propylene glycol)(Mn-2,000) and 2.11 g NMP under a nitrogen atmosphere. 0.064 g ofdibutyltin dilaurate was then added and the mixture was heated to 78-80°C. After 4.5 hours, 4.56 g of glycerin carbonate and 0.93 g NMP wasadded to the reaction mixture with stirring for an additional 4 hours atwhich the reaction was cooled to 70° C. TEA (4.08 g) and NMP (1.9 g)were added with stirring for 20 minutes, at which time the prepolymerwas dispersed into 197 g DIW at ˜42° C. The prepolymer was added over 10minutes followed by an additional 5 minutes mixing at 1000 rpm. A 35.4%solution of HMDA in DIW (4.61 g) was diluted with an additional 10.02 gDIW and added dropwise to the dispersion over 15 minutes. After anadditional 30 minutes a clear, slightly opaque dispersion was isolated.

Example 7 Synthesis of a Polyurethane Dispersion Using a Mixture of EndGroup Monomers, Catalyzed, with Chain Extension AfterDispersion—Glycerin Carbonate/2-Hydroxyethyl Pyrrolidone (HEP) EG(Adhesive G)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 76.40 gpoly(propylene glycol) (Mn-2,000), 9.284 g of Ymer N120 (Perstorp), and4.433 g of DMPA (dimethylolpropionic acid). 31.2 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 0.060 gof dibutyltin dilaurate was then added and the mixture was heated to75-76° C. for 5 hours, after which 4.828 g of a mix of glycerincarbonate (3.35 g) and 2-hydroxyethyl pyrrolidone (3.653 g) was addedand stirred for an additional 3.5 hours. TEA (3.61 g) was added andafter 15 minutes, the prepolymer was dispersed into 202 g DIW at ˜39° C.over 15 minutes followed by an additional 5 minutes mixing at 750 rpm.HMDA (2.09 g) in water (10.0 g) DIW and added dropwise to the dispersionover 10 minutes. After an additional 60 minutes, the clear, translucentdispersion was isolated.

Example 8 Synthesis of a Polyurethane Dispersion Used a StoichiometricMixture of End Group Monomers—Glycerin Carbonate/2-HydroxyethylPyrrolidone (Adhesive H)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 95.50 gpoly(propylene glycol) (Mn-1,000), 9.99 g of Ymer N120 (Perstorp), and7.77 g of DMPA (dimethylolpropionic acid). 54.4 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) was thenadded and the mixture was heated to 75-80° C. for 5 hours, after which10.71 g of a mix of glycerin carbonate (4.43 g) and 2-hydroxyethylpyrrolidone (10.23 g) was added and stirred for an additional 2 hours.The temperature was dropped to 55° C. and mixed for an additional 20hours. The temperature of the reaction was increased to 75° C. at whichtime TEA (4.58 g) was added. After 30 minutes, the prepolymer wasdispersed into 310 g DIW at ˜39° C. The prepolymer was added over 30minutes followed mixing overnight at ambient temperature. A clear,translucent dispersion was isolated.

Example 9 Synthesis of a Polyurethane Dispersion Used a StoichiometricMixture of End Group Monomers—Glycerin Carbonate/2-HydroxyethylPyrrolidone EG (Adhesive J)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 158.3 gpoly(propylene glycol) (Mn-2,000), 10.60 g of Ymer N120 (Perstorp), and10.19 g of DMPA (dimethylolpropionic acid) at 30° C. 58.13 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) was thenadded and the mixture was heated to 100° C. for 5.5 hours. Thetemperature was decreased to 80° C. and 10.60 g of a mix of glycerincarbonate (4.378 g) and 2-hydroxyethyl pyrrolidone (9.552 g) was addedand stirred for an additional 1 hour. The temperature was dropped to 55°C. and mixed for an additional 20 hours. The temperature of the reactionwas decreased to 70° C. and mixed overnight for an additional 21 hours.TEA (7.15 g) was added and after 15 minutes, the prepolymer wasdispersed into 462 g DIW at 50° C. The prepolymer was added over 70minutes at which time the temperature was increased to 65° C. over 1.5hours. After overnight mixing at ambient temperature, a clear,translucent dispersion was isolated.

Example 10 Synthesis of a Polyurethane Dispersion Using aNon-Stoichiometric Mixture of End Group Monomers, Catalyzed, with ChainExtension After Dispersion—2-Hydroxyethylpyrrolidone/3-AminopropylTrimethoxysilane (Adhesive L)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 74.818 gpoly(propylene glycol) (Mn-2,000), 8.515 g of Ymer N120 (Perstorp), and4.054 g of DMPA (dimethylolpropionic acid). 27.435 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 0.057 gof dibutyltin dilaurate was added and the mixture was heated to 76-78°C. for 3.5 hours. 2-Hydroxyethylpyrrolidone (3.034 g) was added and thereaction was heated for an additional 3 hours. TEA (3.628 g) was addedand after 10 minutes, the prepolymer was dispersed into 178 g DIW at˜39° C. over 15 minutes. After an additional 5 minutes mixing at 900rpm, HMDA (2.824 g) in DIW (12.557 g) and 3-aminopropyl trimethoxysilane(1.206 g) were separately added dropwise to the dispersion over 25minutes. After an additional 90 minutes the dispersion was isolated.

Example 11 Synthesis of a Polyurethane Dispersion Using aNon-Stoichiometric Mixture of End Group Monomers, Catalyzed, with ChainExtension After Dispersion—Glycerin Carbonate/3-Hydroxypropionitrile(Adhesive M)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 76.532 gpoly(propylene glycol) (Mn-2,000), 9.148 g of Ymer N120 (Perstorp), and4.129 g of DMPA (dimethylolpropionic acid). 30.024 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) and 0.062 gof dibutyltin dilaurate was added and the mixture was heated to 75-77°C. for 3.5 hours. 3.97 g of a mixture of glycerin carbonate (5.006 g)and 3-hydroxypropionitrile (1.656 g) was added and the reaction washeated for an additional 2.5 hours. TEA (2.75 g) was added and after 15minutes, the prepolymer was dispersed into 176 g DIW at ˜39° C. over 10minutes. With mixing at 750 rpm, HMDA (1.773 g) in DIW (10.0 g) wasadded dropwise to the dispersion over 10 minutes. 64.5 g additional DIWwas added and after an additional 30 minutes the dispersion wasisolated.

Example 12 Synthesis of a Polyurethane Dispersion Used aNon-Stoichiometric Mixture of End Group Monomers, Uncatalyzed, withChain Extension After Dispersion—Glycerin Carbonate/2-HydroxyethylPyrrolidone EG (Adhesive O)

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 200.3 gpoly(propylene glycol) (Mn-2,000), 13.86 g of Ymer N120 (Perstorp), and14.72 g of DMPA (dimethylolpropionic acid) at 30° C. 95.1 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) was thenadded and the mixture was heated to 100° C. for 3.5 hours after whichtime the polymerization was essentially complete (as monitored by mid IRspectroscopy). The temperature was decreased to 80° C. and 16.84 g of amix of glycerin carbonate (6.656 g) and 2-hydroxyethyl pyrrolidone(14.419 g) was added and stirred for an additional 16 hours. Thetemperature was decreased to 78° C. and TEA (10.54 g) was added. After75 minutes, the prepolymer was dispersed into 625 g DIW at 40C over 30minutes, followed by chain extension using a mix of HMDA (5.51 g) in DIW(10.8 g) over an additional 10 minutes. The reaction temperature wasincreased to 55° C. for 1 hour, after which time heating was terminatedand the dispersion mixed under ambient conditions overnight to yield aclear, semi-translucent product.

Example 13 Synthesis of a Polyurethane-Acrylic Hybrid Adhesive A

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 120.0 gpoly(propylene glycol) (Mn-1,000), 12.90 g of Ymer N120 (Perstorp), and9.72 g of DMPA (dimethylolpropionic acid). 68.37 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) was thenadded and the mixture was heated to 100° C. for 4.5 hours. After coolingto 80° C., 11.98 g of a mix of glycerin carbonate (4.24 g) and2-hydroxyethyl pyrrolidone (9.71 g) was added and stirred for 1 hour.The temperature was lowered to 70° C. and mixed for an additional 16.5hours. The temperature of the heating oil was increased to 77° C. atwhich time TEA (6.28 g) was added. After 40 minutes, the prepolymer wasdispersed into 433 g DIW at ˜45° C. over 35 minutes followed by heatingto ˜50° C. for one hour. A clear, translucent polyurethane dispersionwas isolated.

To a 1 1, 3-necked flask was added 265.0 g of the translucentpolyurethane dispersion (35.0% solids), 10.7 g of butyl acrylate, 4.3 gof glycidyl methacrylate and 0.42 g of 4,4′-Azobis(4-cyanovaleric acid).The mix was stirred at 500 rpm for 90 minutes at which time it washeated to 70° C. under a nitrogen atmosphere. An additional 54 grams ofDIW was added and heating was continued for a total of 21 hours. Aftercooling to ambient temperature, the thin, whitish dispersion wascollected.

Example 14 Synthesis of a Polyurethane-Acrylic Hybrid Adhesive B

To a 1 1, 3-necked flask under a nitrogen atmosphere was added 179.4 gpoly(propylene glycol) (Mn--2,000), 6.54 g of Ymer N120 (Perstorp), and15.02 g of DMPA (dimethylolpropionic acid). 72.91 g H12MDI(4,4′-Methylenebis(cyclohexyl isocyanate), hydrogenated MDI) was thenadded and the mixture was heated to 100° C. for 4.5 hours. After coolingto 80° C., 15.71 g of a mix of glycerin carbonate (6.36 g) and2-hydroxyethyl pyrrolidone (13.79 g) was added and stirred for 21 hours.9.65 g of TEA was added and stirred for 2.5 hours, after which time theprepolymer was dispersed into 548 g DIW at 50° C. over 30 minutes. Thedispersion was heated to 60° C. for 1 hour, followed by mixing overnightat ambient temperature. A clear, thin polyurethane dispersion wasisolated.

To a 1 1, 3-necked flask was added 251.5 g of the thin polyurethanedispersion (33% solids), 12.7 g of butyl acrylate, 4.7 g of glycidylmethacrylate, 6.3 g of 2-ethylhexyl methacrylate, 32.8 g DIW and 0.28 gof 4,4′-Azobis(4-cyanovaleric acid). The mix was stirred at 400 rpm for25 minutes at which time it was heated to 70-80° C. under a nitrogenatmosphere for 7.5 hours. 0.12 grams of AIBN was added and mixing wascontinued at 68-70° C. for 19 hours. After cooling to ambienttemperature, the thin, whitish dispersion was collected.

Example 15 General Overcoating Process and Test Display Structures

This example illustrates the general overcoating process and testdisplay structures used in the subsequent examples, unless indicatedotherwise.

Previously coated and dried ink, either on a first release substrate(for 3-layer such as shown in FIG. 1D) or electrode substrate (for2-layer such as shown in FIG. 1C), was coated with adhesive fluid(prepared by mixing the corresponding polyurethane dispersion with aspecified amount of crosslinker(s)) to a specified dry coat weight usingeither a slot-die or linear bar coater. The ink-adhesive coating wasthen oven dried at a specified temperature and residence time, followedby lamination to either an electrode substrate (for 3-layer) or arelease substrate (for 2-layer). For the 3-layer system, the firstrelease substrate was removed from the ink surface which is thenlaminated to a smooth side laminate (SSL) adhesive (e.g., adhesive layer140 in FIG. 1D). The 2-layer structure required no further laminationsteps prior to construction of test structures. Both intermediatestructures (2-layer and 3-layer) are then processed into test displaystructures by cutting appropriately sized sections, removing theremaining release backing and laminating to the appropriate backplaneelectrode. Test display conditioning was typically carried out after 25°C. and 50% relative humidity (RH) conditioning, unless alternateconditions are required.

Example 16 Electro-Optical Performance of Polyurethane Adhesives

Table 1 shows t₀ EO states of cyclic carbonate modified polyurethanesovercoated to one or more types of ink layers compared with acomparative laminate control (an aqueous polyurethane dispersion)laminated to an ink layer in a 3-layer structure. Overcoat wet filmthicknesses were ˜4 mil corresponding to a coat weight of ˜25 g/m². The3-layer pixels were conditioned at 25° C. and 50% RH. Adhesive Ccontains a lower level of cyclic carbonate functionality than AdhesiveB. It was observed that significantly improved white state (WS), darkstate (DS) and dynamic range (DR) L* values were obtained for theexperimental adhesives when compared to the comparative laminate pixel.While the overall dynamic range achieved for the adhesives and controladhesive in Table 1 were relatively similar, it is possible tomanipulate the WS and DS by changing the level of cyclic carbonate asindicated. The level of cyclic carbonate functionality in Adhesive A wasslightly higher than in Adhesive B and explains why it has slightlypoorer WS image stability (see section below). Cyclic carbonatefunctionality also leads to very low DS L* values as exemplified byAdhesive A.

TABLE 1 Init 30 s Init 30 s Init 30 s Adhesive Functionality WS L* WS L*DS L* DS L* DR L* DR L* A Cyclic 73.4 72.8 13.0 13.7 60.4 59.1 carbonateB Cyclic 73.4 73.3 16.5 16.6 56.9 56.7 carbonate C Cyclic 74.5 74.6 17.117.6 57.4 57.0 carbonate control n/a 73.8 73.0 17.8 19.4 56.0 53.6

FIGS. 5A-5B show adjusted 30 s image stability traces of experimentalpolyurethanes overcoated to an ink layer compared to the controladhesive laminated over an ink layer. The 3-layer pixels wereconditioned at 25° C. and 50% RH. FIGS. 5A-5B illustrate the effect thelevel of cyclic carbonate functionality has on the WS and DS 30 s imagestability. Both adhesives lead to minimal WS kickback and have eitherstable WS L* (FIG. 5B), or minimal WS L* improvement, simultaneous withimproved L* values. Similar improved behavior was observed for the DS L*stability, although the increase was slightly greater then observed forthe WS.

Both the magnitude and the direction of WS L* drift can be controlled bythe level of cyclic carbonate functionality incorporated. FIGS. 6-7illustrate this effect. Low levels of cyclic carbonate lead to anincrease in WS L* over time, whereas very high levels result in adecrease in WS L* over 30 seconds. There is a correlation between themol % level of incorporated cyclic carbonate functionality and thedegree of WS L* drift as illustrated in FIG. 8. There was an optimumlevel of cyclic carbonate functionality around 10 mol %.

Example 17 Effect of End Group Type

FIG. 8 illustrates the effect of pyrrolidone versus cyclic carbonateend-capping groups. Both functional groups are 5-membered heterocycleswith either 1 or 2 carbon atoms separating the ring from the oxygenbonded to the polyurethane chain. At equimolar levels of incorporationinto the polyurethane backbone, significantly better image stability wasobserved for the cyclic carbonate containing polyurethane, clearlyillustrating the effect of functionality type.

This effect on to states is shown in Table 2. In the Adhesive B series,the pixel laminated with the comparative laminate (control) exhibits anoverall WS loss from the initial states to 30 s and the pixel overcoatedwith the pyrrolidone containing adhesive exhibits an overall WSimprovement. The 3-layer pixels were conditioned at 25° C. and 50% RHand are from two separate experiments as indicated. The pixel overcoatedwith the cyclic carbonate containing adhesive has a stable WS while atthe same time exhibiting slightly improved WS L* to the laminate system.A similar observation was made in the Adhesive A series, although inthis case the WS L* offset for the laminate pixel was lower. Theimproved DR L* values for all overcoated pixels containing cycliccarbonate functionality, relative to control, were due to significantlyimproved DS L* values.

TABLE 2 Prime End Init 30 s Init 30 s Init 30 s Adhesive Group WS L* WSL* DS L* DS L* DR L* DR L* B Cyclic 73.1 73.1 13.9 14.9 59.2 58.2carbonate L Pyrrolidone 73.0 73.6 14.5 16.1 58.5 57.5 control n/a 72.772.1 16.2 17.0 56.5 55.1 A Cyclic 74.0 74.2 13.9 14.9 60.1 59.3carbonate control n/a 73.4 73.2 16.3 17.1 57.1 56.1

FIG. 9 shows the 240 ms WS L* pulse trace for adhesive M overcoated toan ink layer compared with the comparative laminate laminated to thesame ink. Adhesive M incorporates cyclic carbonate functionality as wellas acid functionality for curing. Both adhesives were coated to ˜25 g/m2utilizing 5 mil thickness electrode. A 3 L* boost in WS was observed forthe overcoated ink (with equal DS L* traces).

Example 18 Direct to ITO Ink Structures

Ink was coated to a transparent, flexible substrate coated with indiumtin oxide. Subsequently, aqueous adhesive formulation containingdispersed polyurethane and carbodiimide crosslinker (to react withcarboxyl functionality in the polyurethane) was bar coated and dried incross draft ovens at elevated temperature. The level of carbodiimidecrosslinker was matched to the level of acid functionality present inthe polyurethane such that the acid/carbodiimide functionality was about1:1.

Table 3 shows initial dynamic range δL* (relative to the comparativelaminate) that vary with end group modification. It was observed thatcomparable initial properties are obtained with carbonate modifiedpolyurethanes relative to the comparative (Control) laminated ink.

TABLE 3 Application δ (DR) CYANO Overcoat −3 PYRROLIDONE Overcoat −1nBUTYL Overcoat −3 CARBAMATE Overcoat −2 CARBONATE Overcoat 0 ControlLaminate 0

FIG. 10 demonstrates WS L* loss over time during 25° C. electricalstress testing of overcoated adhesives on machine coated DTI open ink.Data was relative to t=0 for each individual adhesive. All overcoatedadhesives were crosslinked with a carbodiimide crosslinker at a 1:1acid:carbodiimide equivalency. The comparative laminate (control) wasnot crosslinked and contained 180 ppm ionic dopant. It was unexpectedlyfound that incorporation of pendant cyclic carbonate functionalityresulted in enhanced 25° C. stress degradation resistance that iscomparable to the comparative laminated ink. This behavior was notobserved for other end group modified polyurethanes studied.

Example 19 Improved Low Temperature Performance

Another performance improvement observed with carbonate modifiedpolyurethanes was improved low temperature performance, i.e., switchingbehavior and resulting L* values. Table 4 lists EO data accumulated at0° C. The carbonate modified adhesive exhibited the best switchingbehavior at 0° C.

TABLE 4 WS L* 0 C. DS L* 0 C. DR L* 0 C. CYANO 66.1 31.3 34.8PYRROLIDONE 66.8 33.3 33.4 BUTYL 61.7 34.9 26.8 CARBAMATE 64.3 33 31.3CARBONATE 69.2 21.4 47.7

Examples 20-23 generally relate to low coat weight adhesive films.

Example 20 Low Coat Weight Overcoating

Surprisingly, by manipulating the rheology of the polyurethane and thetype and rate of the cure process, overcoating of ink and subsequentvoid-free lamination to electrode substrates may be achieved usingrelatively low adhesive coat weights. Generally, for adhesives that areutilized in commercial and advanced prototype displays, defects such aslamination voids and orange peel increase as the coat weight decreasesand at least ˜25 g/m2 of material is required to achieve acceptableperformance. The adhesives described herein substantially reduce theamount of material required for void-free lamination and reduced orangepeel.

Table 5 lists coat weight, void count and orange peel forink-adhesive-electrode structures in which adhesive N, containingcarboxylic acid, cyclic carbonate and acrylate functionality, wasovercoated to an ink layer on a release substrate by using a linear barcoater. A dry coat weight of 6 g/m2 (approximately 1 mil wet coatthickness) was achieved by using a 30% solids aqueous adhesiveformulation. As the data indicates, near void-free lamination of theelectrode to the ink surface is achieved. In addition, orange peelvalues are within the range typically observed for current commercialproducts that have adhesive coat weights of 25 g/m2. The characteristicsof the adhesive were selected to balance adhesive Tc (e.g., to influencehow the material flows into the surface of the ink where thinner filmsrequire reduced amounts of adhesive, generally requiring lower adhesiveTc values in order to planarize the electro-optic layer before curing),the extent of crosslinking (acid-carbodiimide), as well as solventevaporation during the first cure to enable flow with filling of therough ink surface and subsequent void-free lamination (e.g., after thesecond cure) to both 5 mil and 1 mil electrode substrate.

TABLE 5 Overcoat Void Count per Size Range Orange Electrode Weight(m(μm) Peel thickness (g/m²) 30-100 100-125 125-150 150+ (Wc) 5 mil 62-3 0 0 0 5-6 1 mil 6 2-3 0 0 0 26-30

Table 5 shows the coat weight, void count and orange peel values forlamination of 5 mil and 1 mil electrode to adhesive N overcoated to anink layer open ink-on-release.

An additional example illustrating the benefit of combiningfunctionality that improves electro-optical states with a dual curingprocess that achieves low coat weights is illustrated in Table 6. Inthis case adhesive M is overcoated to prototype ink on release at a lowand high wet film build (4 mil wet corresponds to ˜20-25 g/m2 and 1.5mil wet corresponds to ˜8-10 g/m2), followed by lamination to 5 milelectrode substrate and construction into 3-layer graphite pixels. Ascan be seen from the data, and the accompanying image stability tracesin FIG. 11, improved WS L* and DR L* values were obtained with theadhesive M: lower coat weights for the overcoated material lead tobetter WS image stability, lower levels of kickback and improvedelectro-optical states. Although the initial DS L* values were higherthan observed for the comparative laminate control, the lower levels ofDS SE result in near equivalent 30 second DS L* values.

TABLE 6 Wet Coat Coat Init 30 s Init 30 s Init 30 s Adhesive ThicknessProcess WS L* WS L* DS L* DS L* DR L* DR L* Control n/a Laminate 73.773.6 16.9 19.7 56.8 54.0 M   4 mil Overcoat 75.5 74.4 20.3 20.3 55.254.0 M 1.5 mil overcoat 75.5 74.9 19.4 20.0 56.2 54.9

Table 6 show 25° C. electro-optical data for adhesive M overcoated toprototype ink on release at a low and high wet film build illustratingthe impact of electro-optically active functionality and a low coatweight adhesive. 3-Layer, pixels were cured at 50° C./50% RH andreconditioned to 25° C./50% RH prior to measurement.

Example 21 Lamination to Open Ink

In this example, the adhesive was applied to either an electrodesubstrate (for example, a 3-layer structure) or to a release substrate(for example, a 2-layer structure) followed by lamination to the inksurface. Secondary curing to achieve final mechanical andelectro-optical property development to both interfaces was then carriedout.

Adhesives B (acid, cyclic carbonate, silane functionality) and AdhesiveL (acid, pyrrolidone, silane functionality), both mixed with acarbodiimide crosslinker (for stage I curing (the first cure), wascoated to release substrate at 1.5 mil wet film build (approximately 7-9g/m2 dry adhesive), dried in a cross draft oven and laminated toprototype ink on 1 mil electrode substrate. The adhesive surface wasdirectly laminated to a carbon backplane, or to commercial SSL, whichwas then laminated to a carbon backplane. Stage II curing (the secondcure) is afforded by the incorporated trimethoxysilane functionality viacondensation mechanisms. As a comparative example, open ink on 1 milelectrode substrate was laminated to SSL (2 layers each at 5 g/m2adhesive weight; 10 g/m2 total coat weight). The SSL was minimallycrosslinked thereby allowing a direct comparison of adhesive rheologyand effects of dual curing on lamination quality. Some void formationwas evident (indirectly observed via switching effects) in thecomparative example whereas the pixels with adhesive B exhibited noevidence of lamination voids when switched. Furthermore, as shown inTable 8, improved WS L* values were obtained with the adhesive B.

TABLE 7 Init 30 s Init 30 s Init 30 s SSL Adhesive End Group WS L* WS L*DS L* DS L* DR L* DR L* None B Cyclic 74.9 74.9 15.4 17.4 59.5 57.5carbonate 1 layer B Cyclic 74.9 75.0 15.3 17.4 59.6 57.6 carbonate NoneL Pyrrolidone 75.0 75.0 15.1 17.1 59.9 57.9 1 layer L Pyrrolidone 74.774.7 15.2 17.6 59.5 57.2 2 layer Control n/a 73.9 73.3 15.3 18.1 58.655.2

Table 7 shows initial and 30 s L* values for 2- or 3-layer DTI pixels ofB and Adhesive L adhesive laminated to prototype ink on 1 mil electrodesubstrate, compared with 2-layer pixels made using two layers ofcommercial SSL (at 5 g/m2 adhesive weight; 10 g/m2 total adhesive coatweight) laminated to prototype ink on 1 mil electrode. Experimentaladhesives were coated to ˜1.5 mil wet bar height on 1 mil electrode,corresponding to ˜7-9 g/m2 dry adhesive.

An additional example of electro-optical improvements that can beobtained by laminating the adhesives is shown in Table 8. In this casethe adhesive was coated at 3.5 mil wet coat thickness to 5 mil electrodesubstrate, dried and laminated to prototype ink on release. Acomparative aqueous polyurethane dispersion (control) was utilized forcomparison. A WS L* of 76 and a DS L* of 18 is observed for the adhesiveat 30 seconds.

TABLE 8 Init 30 s Init 30 s Init 30 s Adhesive Process WS L* WS L* DS L*DS L* DR L* DR L* M Laminate 75.7 75.9 16.3 17.7 59.4 58.2 controlLaminate 74.9 74.9 16.0 18.2 58.9 56.7

Table 8 shows 25° C. t=0 electro-optical data for adhesive M laminatedto prototype open ink compared with the comparative control laminated tothe same ink. Pixels are 3-layer graphite conditioned at 25° C. and 50%RH.

Example 22 Hybrid Adhesive Curing

The rheology profile of a hybrid adhesive A is shown in FIG. 12. Bothpre-cure and post-cure curves are illustrated. In FIG. 12, the shearstorage modulus (G′) and shear loss modulus (G″) are plotted as afunction of temperature for stage I (thermoplastic dry) and stage II(acid-epoxy covalent crosslinking) cured adhesives. The combination of ahigh temperature plateau in the G′, combined with a relatively low tandelta for the crosslinked (cured through stage II) material illustratesthe efficiency of curing. The crossover temperature (Tc) ofpolyurethanes, i.e., the temperature at which tan delta (ratio of lossmodulus to storage modulus) is equal to 1 and the material begins toexhibit more viscous flow, is utilized to estimate the relative easewith which the adhesive planarizes the ink surface during drying andlamination. As can be seen in the plot of tan delta (not shown), thestage I cure (a thermoplastic drying), hybrid adhesive A has a Tcapproximately 10-15° C. higher than the parent, unmodified polyurethane,making it generally suitable for use as a planarization adhesive at lowcoat weights Improved rheology was achieved with the hybrid adhesive,whereas a significantly higher coat weight adhesive layer was requiredin order to efficiently planarize the ink surface using the commercialadhesive.

Application of hybrid adhesive A was conducted by overcoating theadhesive fluid to open ink, drying in a heated oven (stage I cure),laminating a release substrate and subsequent stage II curing (chemicalcrosslinking) enabling the formation of an ink-adhesive coating layerthat was relatively very thin (overall ink-adhesive thickness was about23-24 microns) with a very low level of void defects. Correspondingcommercial ink-adhesive coatings were approximately 40 microns thick.FIGS. 13-14 are SEM micrographs of a cross-section of a 2-layerink-adhesive stack with hybrid adhesive A coated to 8 g/m2 (dry coatweight) demonstrating planarization and relatively defect free (voids)adhesive-ink interface and illustrating the overall thickness of theink-adhesive coating layer. High temperature stress testing of a testglass display made from this front plane laminate (FPL) did not resultin any defect formation confirming sufficient mechanical propertydevelopment after stage II curing.

Example 23 Polyurethane Adhesive with Multiple Crosslinking Reagents

In this example, a relatively low Tc polyurethane is combined with twodifferent crosslinking reagents that differ in relative rates ofcrosslinking with reactive functionality on the polyurethane backbone.Stage I crosslinking was achieved during drying and lamination ofadhesive application providing desirable rheology to enable subsequentprocessing steps. Stage II crosslinking largely occurred during the cureconditioning cycle of the FPL. For example, FIG. 15 illustrates the useof carbodiimide and epoxy crosslinkers with polyurethane (PU) that havesignificantly different crosslinking rates.

A polyurethane dispersion was mixed with 2 wt. % epoxy and 4.8 wt. %carbodiimide overcoated to open ink on PET-ITO, dried and laminated to alow surface energy release substrate. Curing of the carbodiimidecrosslinker was relatively complete after the drying/lamination stageand curing of the epoxy crosslinker subsequently took place at 60 C over5 days. The rheology profile of the adhesive system (Adhesive J) isplotted in FIG. 16. Both pre-cure and post-cure (through stage II)curves are illustrated. In FIG. 16, the shear storage modulus (G′) andshear loss modulus (G″) are plotted as a function of temperature. Thecombination of a high temperature plateau in the G′, combined with arelatively low tan delta for the cured material demonstrates theefficiency of crosslinking. FIGS. 17A-17B are SEM micrographs of across-section of a 2-layer ink-adhesive stack with Adhesive J coated at7 g/m² demonstrating planarization and relatively defect free (voids)adhesive-ink interface and illustrating the overall thickness of theink-adhesive coating layer. High temperature stress testing of a testglass display made from this FPL did not result in any defect formationconfirming sufficient mechanical property development aftercrosslinking.

Example 24 Dual Cure Adhesive with Two Cross-Linking Reagents

The following example demonstrates a dual cure incorporating twocrosslinking-based cures.

The adhesive used a synthesis of a polyurethane dispersion with amixture of end group monomers—Glycerin Carbonate/2-Hydroxyethylpyrrolidone such as Adhesive J. The dual (covalent) crosslinking cureutilized the carboxylic acid functionality on the polyurethane to reactwith carbodiimide and epoxy crosslinkers. The following amounts ofcrosslinkers were used with Adhesive J:

Sample I: Sample I: 4.8 wt. % carbodiimide crosslinker (single cure)

Sample II: 8.0 wt. % carbodiimide crosslinker (single cure)

Sample III: 4.8 wt. % carbodiimide crosslinker+2.1 wt. % epoxycrosslinker (dual cure)

Sample IV: 8.0 wt. % carbodiimide crosslinker+1.0 wt. % epoxycrosslinker (dual cure)

Using the methods described above, cross-linker consumption wasmonitored during Stage I curing (oven drying+ambient hold+hotlamination). The loss of carbodiimide functionality at ambienttemperature for Samples I and II, after oven drying of the coatedadhesive fluid, was plotted as a function of time. The ratio ofcarbodiimide peak area to CH peak area was then used to quantify theloss of carbodiimide. The residual level of carbodiimide after 2 hoursis a function of the initial level of carbodiimide, but was relativelylow in both samples. This illustrates that by the end of Stage I curing(oven drying+ambient hold+hot lamination), essentially completeconsumption of carbodiimide crosslinker has occurred, even at the higherof the two levels of carbodiimide, prior to Stage II curing.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations may depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All patent applications and patents incorporated herein by reference areincorporated by reference in their entirety. In case of conflict, thepresent specification, including definitions, will control. In caseswhere the present specification and a document incorporated by referenceinclude conflicting and/or inconsistent disclosure, the presentspecification shall control. If two or more documents incorporated byreference include conflicting and/or inconsistent disclosure withrespect to each other, then the document having the later effective dateshall control.

The indefinite articles “a” and “an,” as used herein, unless clearlyindicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein, should be understood to mean“either or both” of the elements so conjoined, i.e. elements that areconjunctively present in some cases and disjunctively present in othercases. Other elements may optionally be present other than the elementsspecifically identified by the “and/or” clause, whether related orunrelated to those elements specifically identified unless clearlyindicated to the contrary. Thus, as a non-limiting example, a referenceto “A and/or B,” when used in conjunction with open-ended language suchas “comprising” can refer, in one embodiment, to A without B (optionallyincluding elements other than B); in another embodiment, to B without A(optionally including elements other than A); in yet another embodiment,to both A and B (optionally including other elements); etc.

As used herein, “or” should be understood to have the same meaning as“and/or” as defined above. For example, when separating items in a list,“or” or “and/or” shall be interpreted as being inclusive, i.e. theinclusion of at least one, but also including more than one, of a numberor list of elements, and, optionally, additional unlisted items. Onlyterms clearly indicated to the contrary, such as “only one of or“exactly one of,” or, when used in the claims, “consisting of,” willrefer to the inclusion of exactly one element or a list of elements. Ingeneral, the term “or” as used herein shall only be interpreted asindicating exclusive alternatives (i.e. “one or the other but not both”)when preceded by terms of exclusivity, such as “either,” “one of,” “onlyone of,” or “exactly one of.” “Consisting essentially of,” when used inthe claims, shall have its ordinary meaning as used in the field ofpatent law.

1. An electro-optic assembly comprising a polyurethane layer includingan end-capping cyclic carbonate of Formula (XII):

wherein: R¹ is selected from the group consisting of hydrogen,optionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted aryl, optionally substituted heteroaryl,optionally substituted halide, and optionally substituted hydroxyl; L isa linking group, optionally absent; n is 1-4; and

represents the location of a bond to the polyurethane.
 2. Theelectro-optic assembly of claim 1, wherein L is optionally substitutedalkylene or optionally substituted heteroalkylene.
 3. The electro-opticassembly of claim 1, wherein R¹ is hydrogen.
 4. The electro-opticassembly of claim 1, wherein the polyurethane layer further comprises asecond type of end-capping group.
 5. The electro-optic assembly of claim4, wherein the second type of end-capping group comprises a pyrrolidone.6. The electro-optic assembly of claim 5, wherein the pyrrolidonecomprises Formula (XVI):

wherein: each R² is the same or different and is selected from the groupconsisting of hydrogen, optionally substituted alkyl, optionallysubstituted heteroalkyl, optionally substituted aryl, optionallysubstituted heteroaryl; M is a linking group, optionally absent; and

represents the location of a bond to the polyurethane.
 7. Theelectro-optic assembly of claim 6, wherein M is optionally substitutedalkylene or optionally substituted heteroalkylene.
 8. The electro-opticassembly of claim 4, wherein the second-type of end capping groupcomprising a silane of Formula (XXXIII):

wherein: L is a linking group, optionally absent; each R³ is the same ordifferent and comprises —(CH₂)_(n)— or —O—(CH₂)_(n); each n is the sameor different and 1-4; and

represents the location of a bond to the polyurethane.
 9. Theelectro-optic assembly of claim 8, wherein L is optionally substitutedalkylene or optionally substituted heteroalkylene.
 10. The electro-opticassembly of claim 4, wherein the ratio of the cyclic carbonateend-capping group to the second type of end capping group is between 1:2and 2:1.
 11. The electro-optic assembly of claim 1, wherein thepolyurethane is formed by reaction of a diisocyanate compound and atleast one type of diol, and reaction with a cyclic carbonate end-cappingreagent.
 12. The electro-optic assembly of claim 11, wherein thediisocyanate is 4,4′-methylenebis(cyclohexylisocyanate).
 13. Theelectro-optic assembly of claim 5, wherein the polyurethane is formed byreaction of a diisocyanate compound and at least one type of diol,followed by reaction with a cyclic carbonate end-capping reagent and asecond type of end-capping reagent comprising a pyrrolidone.
 14. Theelectro-optic assembly of claim 13, wherein the diisocyanate is4,4′-methylenebis(cyclohexylisocyanate).
 15. The electro-optic assemblyof claim 1, wherein the end-capping cyclic carbonate is provided in aweight percent between about 2 wt. % and about 10 wt. % versus the totalcomposition not including any solvent.
 16. The electro-optic assembly ofclaim 1, wherein the end-capping cyclic carbonate is provided at about5-15 mole % of polyurethane.
 17. The electro-optic assembly of claim 4,wherein the end-capping reagents are provided in a weight percent in anamount between about 2 wt. % and about 10 wt. % versus the totalcomposition not including any solvent.
 18. An electro-optic displaycomprising the electro-optic assembly of claim
 1. 19. The electro-opticdisplay of claim 18, wherein the electro-optic medium comprises anencapsulated electrophoretic medium.
 20. An electro-optic displaycomprising the electro-optic assembly of claim
 4. 21. The electro-opticdisplay of claim 20, wherein the electro-optic medium comprises anencapsulated electrophoretic medium.